WO2010016456A1

WO2010016456A1 - Optical film, process for producing same, polarizer employing optical film, and display device

Info

Publication number: WO2010016456A1
Application number: PCT/JP2009/063735
Authority: WO
Inventors: 忠浩金子; 森田　亮
Original assignee: コニカミノルタオプト株式会社
Priority date: 2008-08-07
Filing date: 2009-08-03
Publication date: 2010-02-11
Also published as: JPWO2010016456A1; KR20110039549A

Abstract

An optical film formed by the melt casting method is provided which eliminates the cast-film deterioration in releasability caused by an increase in film formation rate and which has improved releasability (strippability), has optical properties including excellent transparency and excellent flatness, and can meet demands for thickness reduction, width increase, and quality improvement in protective films for polarizers, etc. Also provided are: a process for producing the optical film; a polarizer employing the optical film; and a display device. The process is for producing an optical film by the melt casting method and comprises: a step in which a resin melt comprising a thermoplastic resin and an additive is cast on the surface of a metallic support to form a cast film; a step in which the cast film is cooled and solidified and then is stripped from the metallic support; and a step in which a surface treatment film is formed on the surface of the metallic support almost over the whole width of the metallic support by conducting a treatment with ordinary-pressure plasma application or with excimer ultraviolet irradiation in the presence of the vapor of the additive and the gas for use in the ordinary-pressure plasma application or excimer ultraviolet irradiation.

Description

Optical film, manufacturing method thereof, polarizing plate using optical film, and display device

The present invention provides an optical film that can be used for various functional films such as a protective film for a polarizing plate used in a liquid crystal display (LCD), a retardation film, a viewing angle widening film, and an antireflection film used in a plasma display. The present invention relates to a method, an optical film, a polarizing plate, and a display device.

In recent years, liquid crystal display devices have come to be used in televisions and large monitors due to improvements in image quality and high definition technology. In particular, these liquid crystal display devices are costly due to their large size and efficient production. The demand for down and the like has become stronger in materials for liquid crystal display devices, and a wider optical film is required.

In recent years, the demand for optical films has been increasing rapidly in response to the rapid growth of liquid crystal TVs, and there is a strong demand for improved productivity.

Optical film production methods are roughly classified into a melt casting film forming method and a solution casting film forming method. The former is a method in which a polymer is heated and melted, the melt is cast on a support and cooled and solidified, then peeled off from the support, and further stretched as necessary to produce a film. In the latter, the polymer is dissolved in a solvent, the solution (dope) is cast on a support, the solvent is evaporated with hot air, hot water, etc., then peeled off from the support, and further stretched as necessary. This is a method for producing a film.

The solution casting film forming method uses a large amount of solvent, whereas the melt casting film forming method does not use a solvent, so it can take a production rate that does not depend on the drying rate and can be expected to improve productivity. .

Here, because the thermal stability of the resin itself is low, in natural polymers such as cellulose, additives such as plasticizers, ultraviolet absorbers, retardation control agents, peelability improvers, antioxidants, thermal decomposition inhibitors Etc. are added in large quantities, and these evaporate from the surface of the hot film coming out of the casting die.

Here, when the film forming speed is low, the film temperature is lowered before the cast film reaches the cooling support, and thus the evaporation of the additive is also suppressed.

On the other hand, when the film forming speed is increased, the high-temperature cast film coming out of the casting die reaches the cooling support before the temperature is lowered, and the additive evaporated from the film is applied to the cooling support surface. Condensate. In that portion, there was a problem that the peeling force of the cast film from the cooling support increased and the peeling deteriorated.

As a result, a force is required for peeling, and a peeling stress is applied to the cast film, resulting in a minute horizontal step deformation.

As described above, conventionally, there has been a problem that the film has to be formed at a low production rate due to the deterioration of the peelability of the cooling support.

Patent Document 1 discloses a method and apparatus for producing resin-coated (laminated) paper, and particularly cleaning a cooling roll that removes low-molecular components adhering to the cooling roll in a laminator apparatus including a step of coating a molten resin. A method is disclosed, and a method of applying energy to the surface of the cooling roll using a high-power laser light source or a flame of a flame burner is described as a cleaning method.

Further, Patent Document 2 discloses a method of removing deposits on the roll surface by irradiating the roll surface used for film production with ultraviolet rays.

Further, in Patent Document 3, plasma is applied to a cooling roll that is in contact with a traveling film in order to reduce film surface scratches generated in the process of forming a thermoplastic resin film and to clean dirt adhered to the cooling roll. A method for removing organic substances adhering to a cooling roll by irradiation is disclosed.

JP 2002-240125 A JP 2003-89142 A JP 2001-62911 A

However, all of the methods described in Patent Documents 1 to 3 are for cleaning a roll, and even in a roll whose surface has been cleaned by such a conventional cleaning method, If a web whose surface is contaminated by the bleed-out of the additive is conveyed, the additive adheres to the roll, and an increase in the peeling force occurs at the part where the additive adheres, and the film deforms at the time of peeling. There is a high risk of making.

When such a peeling stress is applied to cause a minute deformation on the film surface, the deformation itself also causes a deterioration of the smoothness of the film, so that there has been a problem that it cannot be adapted to the recent high-definition and high-quality liquid crystal screens. .

Also, in the part where the peel stress increased, the optical / mechanical properties of the film also differed from the part where the peel stress did not increase, resulting in a difference in retardation value and a corresponding increase in transmittance in the crossed Nicols state (CNT) As a result, there is a problem that unevenness of black pattern due to variation in contrast when the liquid crystal panel is formed, and haze increase.

Furthermore, when applying an antireflection layer, a reduction layer, a hardened surface layer, etc. to the surface of the optical film, repelling failure may occur due to different wettability from the surroundings, or the coating layer may become uneven. There was a problem that it was easy to do.

The object of the present invention is to solve the above-mentioned problems of the prior art, and in the method for producing an optical film by the melt casting film forming method, when the film forming speed is increased, the additive vapor is condensed on the cooling support. It is to improve the productivity by eliminating the deterioration of the peelability of the cast film that occurs in the above.

Furthermore, by improving the releasability (peelability) of the film from the cooling support, by manufacturing an optical film having optical properties excellent in transparency and flatness, a thin film such as a protective film for polarizing plates An object of the present invention is to provide an optical film, a method for producing the same, a polarizing plate using the optical film, and a display device that can meet demands for increasing the width, width, and quality.

In order to solve the above problems, the present invention has the following features.

1. A method for producing an optical film by a melt casting film forming method, comprising: casting a resin melt containing a thermoplastic resin and an additive on a surface of a metal support to form a casting film; and After the film is cooled and solidified, it is peeled off from the metal support, and is carried out in the presence of the additive vapor and a gas used for normal pressure plasma irradiation or excimer ultraviolet irradiation. And a step of forming a surface treatment film on the surface of the metal support over substantially the entire width of the metal support by irradiation treatment.

2. The step of forming a surface treatment film on the surface of the metal support is performed before casting the resin melt on the surface of the metal support, and after forming the surface treatment film on the surface of the metal support in advance. The method for producing an optical film as described in 1 above, wherein the cast film is formed.

3. The step of forming a surface treatment film on the surface of the metal support includes the step of casting the resin melt on the surface of the metal support in a non-passing section of the casting film on the surface of the metal support. 2. The method for producing an optical film as described in 1 above, which is carried out simultaneously.

4. The position where the atmospheric pressure plasma irradiation treatment or the excimer ultraviolet irradiation treatment is performed is near the position where the vapor of the additive is present and the resin solution is cast on the surface of the metal support. The method for producing an optical film as described in 2 above.

5. 5. The method for producing an optical film as described in any one of 1 to 4, wherein the vapor is a vapor of a plasticizer or an ultraviolet absorber.

6). In the normal temperature plasma irradiation treatment, the power supplied between the electrodes is 1 W / cm ² or more and 50 W / cm ² or less (area in which discharge occurs) as treatment conditions. The manufacturing method of the optical film of any one of these.

7). 6. The optical system according to any one of 1 to 5, wherein the excimer ultraviolet irradiation treatment is performed by irradiating ultraviolet light having a dominant wavelength of 172 nm with a light amount of 1 to 3,000 mJ / cm ² as a processing condition. A method for producing a film.

8. 8. The method for producing an optical film according to any one of 1 to 7, wherein the surface treatment film has a contact angle of 5 to 40 degrees between the surface treatment film and water.

9. 9. The method for producing an optical film according to any one of 1 to 8, wherein the thermoplastic resin is a cellulose ester resin.

10. 10. The method for producing an optical film as described in any one of 1 to 9 above, wherein the metal support is any one of an endless belt, a drum, and a roll for film formation.

11. The minimum amount of increase in peeling force necessary to peel the cast film after cooling from the surface of the metal support is 0.1 to 2 at the start of film formation and after 24 hours from film formation. It is in the range of 2.0 (N / m), The manufacturing method of the optical film of any one of said 1-10 characterized by the above-mentioned.

12. An optical film manufactured by the method for manufacturing an optical film according to any one of 1 to 11 above.

13. 13. The optical film as described in 12 above, wherein variation in transmittance at a wavelength of 600 nm at the time of crossed Nicol is in a range of 2 × 10 ⁻⁵ to 60 × 10 ⁻⁵ (%). .

14. A polarizing plate having the optical film according to 12 or 13 on at least one surface.

15. A display device using the polarizing plate described in 14 above.

According to the optical film manufacturing method of the first aspect of the present invention, a decomposition product of an additive such as a plasticizer is a constituent component on the surface of the metal support by performing atmospheric pressure plasma irradiation treatment or excimer ultraviolet irradiation treatment. A very dense surface-treated film is formed, and the presence of the surface-treated film significantly improves the mold releasability (peelability) of the film from the surface of the metal support, resulting in extremely smooth peelability. While the variation in the width direction of the position is reduced, the variation of the retardation (Re) value is greatly reduced, and an optical film having optical characteristics with excellent transparency and flatness can be manufactured, and the production speed The film productivity can be improved, and as a result, it is possible to meet the recent demands for thinning, widening, and high quality of protective films for polarizing plates. The effect say.

According to the invention of the optical film of claim 12, the releasability (peelability) of the film from the metal support is improved, very smooth peelability is obtained, and fluctuation in the width direction of the peel position is reduced. Therefore, the optical film has the effect that the variation in retardation (Re) value in the width direction and the longitudinal direction of the optical film is greatly reduced, and the transparency and flatness are excellent.

According to the invention of the polarizing plate of claim 14, variation in retardation (Re) value is greatly reduced, and the optical film according to claim 12 or 13 excellent in transparency and flatness is provided on at least one surface. Therefore, the polarizing plate also has the effect that the variation in retardation (Re) value is reduced and the transparency and flatness are excellent.

According to the invention of the display device of claim 15, since the variation in retardation (Re) value is reduced, and the polarizing plate according to claim 14 is excellent in transparency and flatness, There is an effect that the contrast is excellent and the visibility is excellent without causing a decrease in contrast and density unevenness.

By the above effects of the present invention, a method for producing an optical film that can meet the demands for thinning, widening, and improving the quality of an optical film as a protective film for a polarizing plate and the like, and the method Can provide a high-quality optical film, a polarizing plate using the optical film, and a display device.

It is a flow sheet which shows embodiment of the apparatus which enforces the manufacturing method of the optical film by the melt casting film forming method in this invention. It is explanatory drawing for demonstrating the principle of the atmospheric pressure plasma irradiation apparatus used in the manufacturing method of the optical film of this invention. It is explanatory drawing for demonstrating the principle of the excimer ultraviolet irradiation apparatus used in the manufacturing method of the optical film of this invention.

Next, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited thereto.

FIG. 1 is a flow sheet showing an embodiment of an apparatus for carrying out the method for producing an optical film of the present invention by a melt casting film forming method.

The present invention relates to a method for producing an optical film by a melt casting film forming method, wherein a resin melt containing a thermoplastic resin and an additive is fed from a casting die (4) to a metal support comprising a first cooling roll ( 5) Casting process for casting on the surface to form a casting film (web) (10), and a process for separating the casting film (10) from the metal support (5) after cooling and solidifying. The surface of the metal support over substantially the entire width of the metal support by the atmospheric pressure plasma irradiation process or the excimer ultraviolet irradiation process performed in the presence of the additive vapor and the gas used for atmospheric pressure plasma irradiation or excimer ultraviolet irradiation. And a step of forming a surface treatment film.

In FIG. 1, the casting film on the surface of the metal support (5) made of the first cooling roll is formed during film formation (the casting process and the process for forming the surface treatment film are simultaneously performed). In the non-passing section, in the presence of the vapor of the additive and the gas used for atmospheric pressure plasma irradiation or excimer ultraviolet irradiation, atmospheric pressure plasma irradiation treatment or excimer ultraviolet irradiation treatment is performed over substantially the entire width of the metal support (5). A surface treatment film is formed on the surface of the metal support (5) by performing high-energy irradiation treatment with an atmospheric pressure plasma irradiation treatment apparatus (21) or an excimer ultraviolet irradiation apparatus (22), and then the metal support (5 ) The resin melt is cast on the surface.

That is, according to the method of the present invention, the surface of the metal support (5) made of the first cooling roll is formed on the surface of the metal support (5) made of the first cooling roll on the surface of the metal support (5) made of the first cooling roll. In the non-passing section [section in which the surface of the metal support (5) is exposed during film formation], in the presence of the additive vapor, the atmospheric pressure plasma irradiation processing apparatus (21) or the excimer ultraviolet irradiation apparatus (22). The surface of the metal support (5) made of the first cooling roll is modified by applying a high energy irradiation treatment, and the resin melt is cast on the surface of the metal support (5) after the modification. is there.

Although not shown, in another embodiment of the method for producing an optical film of the present invention, a resin melt containing a thermoplastic resin and an additive is flowed in the method for producing an optical film by the melt casting method. Before extending, the atmospheric pressure plasma irradiation treatment device (21) or the excimer ultraviolet ray is formed over substantially the entire width of the metal support (5) in the presence of the vapor of the additive and the gas used for atmospheric pressure plasma irradiation or excimer ultraviolet irradiation. By applying high energy irradiation treatment with an irradiation device (22), a surface treatment film is formed on the surface of the metal support (5), and then a resin melt is cast on the surface of the metal support (5). is there.

That is, according to the method of another embodiment of the present invention, the surface of the metal support (5) made of the first cooling roll is so-called off-line before casting the resin melt from the first cooling roll. An atmospheric pressure plasma irradiation treatment device (21) or an excimer ultraviolet irradiation device (21) or an excimer ultraviolet irradiation device (5) in the presence of vapor of the additive and a gas used for atmospheric pressure plasma irradiation or excimer ultraviolet irradiation over substantially the entire surface of the metal support (5). 22), the surface of the metal support (5) made of the first cooling roll is modified by applying the high energy irradiation treatment, and the resin melt is cast on the surface of the modified metal support (5). Is.

In this case, the additive vapor mainly means the vapor of the plasticizer or ultraviolet absorber contained in the resin melt. The atmospheric pressure plasma irradiation process or the excimer ultraviolet irradiation process is performed in the presence of an additive vapor.

In addition, before casting the resin melt, the surface of the metal support (5) is subjected to high-energy irradiation treatment by an atmospheric pressure plasma irradiation treatment device (21) or an excimer ultraviolet irradiation device (22) in a so-called off-line manner. In this case, for example, a plasticizer or an ultraviolet absorber is put into a hot air generator, and hot air is blown from the hot air generator to heat and volatilize the plasticizer or the ultraviolet absorber vapor. It may be possible to blow normal pressure plasma irradiation equipment or excimer ultraviolet irradiation equipment through a duct wrapped with a heat insulating material, and perform atmospheric pressure plasma irradiation treatment or excimer ultraviolet irradiation treatment in the presence of additive vapor. It is done.

Further, the gas used for the atmospheric pressure plasma irradiation treatment or the excimer ultraviolet irradiation treatment means a reactive gas used for the atmospheric pressure plasma irradiation apparatus (21), and in the case of the excimer ultraviolet irradiation apparatus (22). Means a purge gas such as nitrogen gas used for this.

In the present invention, atmospheric pressure plasma irradiation or excimer ultraviolet irradiation is performed in the presence of both an additive vapor and a gas used for atmospheric pressure plasma irradiation processing or excimer ultraviolet irradiation treatment.

Therefore, when performing the atmospheric pressure plasma irradiation process or the excimer ultraviolet irradiation process online, the position where the atmospheric pressure plasma irradiation process or the excimer ultraviolet irradiation process is performed is a lot of the additive vapor, the resin solution is It is preferable that it is the vicinity of the position cast on the surface of a metal support body.

FIG. 2 is an explanatory diagram for explaining the structure of an atmospheric pressure plasma irradiation apparatus used for carrying out the method for producing an optical film of the present invention.

The atmospheric pressure plasma irradiation device (21) discharges the reactive gas by applying a high-frequency voltage between the opposing electrodes, thereby bringing the reactive gas into a plasma state. And the web surface is modified.

The atmospheric pressure plasma method is roughly divided into two types. One is called a direct method or a planar method. A high-frequency power is applied between electrodes arranged opposite to each other so as to sandwich an object to be processed. Is converted into plasma. Another method is called a remote method or a downstream method, in which a reactive gas is introduced through an electrode to which a high-frequency voltage is applied and is turned into plasma. Any of the above schemes can be used in the present invention.

FIG. 2 shows an atmospheric pressure plasma apparatus of the type called the above-described remote system or downstream system.

In the same figure, (a) and (b) are counter electrodes of the atmospheric pressure plasma irradiation device (21), (g) is a reactive gas, (d) is a metal support comprising a first cooling roll from the plasma injection slit ( 5) A gap to the surface.

As a simple structure of the atmospheric pressure plasma irradiation device (21), a reactive gas (g: also referred to as source gas) is introduced and passed between the counter electrodes (a) and (b) to which a high frequency voltage is applied. It is turned into plasma and sprayed onto the surface of the metal support (5) made of the first cooling roll to form a surface treatment film.

In the present embodiment, it is necessary to employ an electrode capable of maintaining a uniform glow discharge state by applying such a high power voltage in the atmospheric pressure plasma irradiation apparatus (21).

Such an electrode is preferably a metal base material coated with a dielectric. It is preferable to coat a dielectric on at least one side of the opposed application electrode and the ground electrode, and more preferably coat both of the opposed application electrode and the ground electrode with a dielectric. The dielectric is preferably an inorganic substance having a relative dielectric constant of 6 to 45. Examples of such a dielectric include ceramics such as alumina and silicon nitride, silicate glass, borate glass, and the like. Glass lining material and the like.

In addition, when a cellulose ester film, which is a transparent film base material, is placed between electrodes or transported between electrodes and exposed to plasma, the transparent film base material has a roll electrode specification that can be transported in contact with one electrode. In addition, the dielectric surface is polished and the electrode surface roughness Rmax (specified in JIS B 0601) is set to 10 μm or less to keep the dielectric thickness and the gap between the electrodes constant. It is possible to stabilize the discharge state, eliminate distortion and cracking due to thermal shrinkage difference and residual stress, and greatly improve durability by covering with non-porous high precision inorganic dielectric. preferable.

If the gap (d) between the blow slit for supplying plasma and the surface of the metal support (5) made of the first cooling roll is too close, it will contact the atmospheric pressure plasma irradiation device (21) due to web curl or the like. The web is scratched, and on the other hand, if it is too far away, the radicals of the plasma cannot reach sufficiently, and the volatile vapor decomposition of the additive and the modification of the web surface cannot be sufficiently performed. 2 to 20 mm is more preferable.

In addition, as the source gas (g), various materials such as nitrogen, oxygen, argon, and helium can be used, but nitrogen is preferable from the viewpoints of environment, exhaust after-treatment, and running cost. Furthermore, it is more preferable to mix a small amount of oxygen with nitrogen. The mixing ratio of oxygen is preferably 5% by volume or less with respect to the volume of the source gas.

Also, the source gas flow rate of atmospheric pressure plasma is desirably 20 to 5000 L / min per 1 m of plasma width. Further, 40 to 2500 L / min is more preferable. In addition, it is desirable to exhaust the cracked gas by providing an exhaust device near the atmospheric pressure plasma irradiation device (21).

In addition, the position where the atmospheric pressure plasma irradiation treatment is performed (the position where the reactive gas g is supplied to the metal support) is a position where a large amount of the additive vapor exists and the resin solution is cast on the surface of the metal support. It is preferable that it is near. Specifically, referring to FIG. 2, when the metal support is in the form of a roll like the first cooling roll 5, the position P <b> 1 where the atmospheric pressure plasma irradiation treatment is performed and the center point of the first cooling roll 5. An angle θ formed by a line L1 when connected to P3, a position P2 where the resin solution is cast onto the surface of the metal support, and a line L2 when connected to the center point P3 of the first cooling roll 5 is 120 °. The following is preferred. When the angle is 120 ° or less, a large amount of the additive vapor is present, and a uniform surface treatment film can be formed on the surface of the metal support.

As processing conditions for the room temperature plasma treatment, it is preferable that the power supplied between the electrodes is 1 W / cm ² or more and 50 W / cm ² or less (area in which discharge occurs). By setting the treatment conditions within this range, it is preferable in that sufficient surface treatment can be performed without causing abnormal discharge such as arc discharge.

FIG. 3 is an explanatory diagram for explaining the principle of the excimer ultraviolet irradiation device (22) used in the method for producing an optical film of the present invention.

In the figure, (u) is an excimer ultraviolet lamp, (r) is a reflector, (p) is a purge gas, (d) is an excimer ultraviolet lamp (u) to a metal support (5) comprising a first cooling roll. It is a gap.

In the present embodiment, various ultraviolet irradiation devices can be used, and the wavelength is particularly preferably 250 nm or less. Under such ultraviolet irradiation, the oxygen contained in the purge gas (p) generates active oxygen and ozone, and decomposes the volatile vapor of the additive into carbon dioxide, water, etc. together with the ultraviolet rays, and also comprises the first cooling roll. The surface of the metal support (5) is modified.

Further, if the gap (d) between the ultraviolet lamp (u) and the metal support (5) made of the first cooling roll is too close, the web may be curled or the like to contact the ultraviolet lamp device and scratch the web. If it is too far away, the ultraviolet light is absorbed by oxygen and the volatile vapor of the additive cannot be decomposed and the surface of the web cannot be sufficiently modified, so that it is preferably about 1 to 20 mm, and more preferably 2 to 15 mm. It is desirable to provide an exhaust device near the ultraviolet irradiation device (22) to exhaust the decomposition gas.

Further, the position where the excimer ultraviolet irradiation treatment is performed is preferably in the vicinity of the position where a large amount of the additive vapor exists and where the resin solution is cast onto the surface of the metal support. Specifically, referring to FIG. 3, when the metal support is in a roll shape like the first cooling roll 5, a position P <b> 1 (a central position irradiated with an ultraviolet lamp) for performing excimer ultraviolet irradiation treatment and Line L1 when connecting the center point P3 of the first cooling roll 5, and line when connecting the position P2 where the resin solution is cast onto the surface of the metal support and the center point P3 of the first cooling roll 5 The angle θ formed by L2 is preferably 120 ° or less. When the angle is 120 ° or less, a large amount of the additive vapor is present, and a uniform surface treatment film can be formed on the surface of the metal support.

Further, as the processing conditions of the excimer ultraviolet treatment, it is preferable to irradiate ultraviolet rays having a dominant wavelength of 172 nm with a light amount of 1 to 3,000 mJ / cm ² . By setting the treatment conditions within this range, it is preferable in that a sufficient surface treatment effect can be obtained in a short time.

The method for producing an optical film according to the present invention includes a step of casting a resin melt containing a thermoplastic resin and an additive on the surface of a metal support (5) made of a first cooling roll to form a cast film, After the casting film is cooled and solidified, it comprises the first cooling roll in the presence of the step of peeling from the metal support (5), the vapor of the additive, and the gas used for atmospheric pressure plasma irradiation or excimer ultraviolet irradiation. A step of forming a surface treatment film on the surface of the metal support (5) made of the first cooling roll by performing atmospheric pressure plasma irradiation treatment or excimer ultraviolet irradiation treatment over substantially the entire width of the metal support (5). It is. Further, the step of forming the surface treatment film on the surface of the metal support (5) made of the first cooling roll may be performed online or offline. According to the method of the present invention, by performing atmospheric pressure plasma irradiation treatment or excimer ultraviolet irradiation treatment in the presence of the vapor of the additive and the gas used for atmospheric pressure plasma irradiation or excimer ultraviolet irradiation, the first cooling roll The surface of the metal support (5) is formed with a very dense surface treatment film comprising a decomposition product of an additive such as a plasticizer as a constituent component. The releasability (peelability) of the film from the film is remarkably improved, a very smooth peelability is obtained, the fluctuation in the width direction of the peel position is reduced, and the film width direction and longitudinal direction retardation (Re ) Value variation can be greatly reduced, and an optical film having optical properties with excellent transparency and flatness can be produced, and the production speed can be increased. It is possible to improve the productivity, and thus the recent thin protective film such as a polarizing plate, in which it is possible to meet demand for broadening, and higher quality.

In the optical film manufacturing method according to the present invention, as described above, plasma irradiation or ultraviolet irradiation is performed in the presence of an additive vapor and a gas used for atmospheric pressure plasma irradiation processing or excimer ultraviolet irradiation processing. According to the method of the present invention, the surface of the metal support (5) made of the first cooling roll has a decomposition product of an additive such as a plasticizer as a constituent component. A dense surface-treated film is formed, and the presence of the surface-treated film significantly improves the releasability (peelability) of the film from the surface of the metal support (5), and from the surface of the metal support (5). The releasability (peelability) of the film is less likely to deteriorate even during long-term film formation, and the effect is further sustained. Moreover, even if the component of the surface treatment film is slightly transferred from the surface of the metal support (5) to the film, it is an additive that has been originally added to the film, so that it hardly affects the film characteristics.

According to the method for producing an optical film of the present invention, the surface treatment film formed on the surface of the metal support (5) has a contact angle of 5 to 40 degrees between the treatment film and water. ,preferable.

In the illustrated embodiment, the metal support (5) is composed of a cooling roll, but the metal support (5) used in the method for producing an optical film of the present invention is also an endless film-forming device. It may be a belt or a drum.

Further, according to the method for producing an optical film according to the present invention, the minimum amount of increase in peeling force required to peel the cast film after cooling from the surface of the metal support is the same as that at the start of film formation. It is preferably within the range of 0.1 to 2.0 (N / m) after 24 hours from the film formation.

According to the optical film produced by the method for producing an optical film of the present invention, the release property (peelability) of the film from the metal support (5) is improved, and a very smooth peelability is obtained. Since the variation in the width direction of the position is reduced, the optical film is excellent in transparency and flatness because the variation in retardation (Re) value in the width direction and the longitudinal direction is greatly reduced.

Further, the dispersion of the transmittance at a wavelength of 600 nm at the time of crossed Nicol of the optical film manufactured by the method for manufacturing an optical film of the present invention is in the range of 2 × 10 ⁻⁵ to 60 × 10 ⁻⁵ (%). Is preferred. Thereby, when incorporated in a liquid crystal panel, the entire screen can be uniformly high in contrast.

According to the method for producing an optical film of the present invention, it is possible to meet demands for thinning, widening, and high quality of an optical film as a protective film for a polarizing plate, etc., and high quality optical with high productivity. A method for producing a film can be provided.

Next, the method for producing an optical film by the melt casting method of the present invention will be described in detail.

As shown in FIG. 1, for example, a cellulose ester resin dried under hot air, vacuum or reduced pressure is melted at an extrusion temperature of about 200 to 300 ° C. using an extruder (1), and a leaf disk type filter (2) Filter through to remove foreign matter. In addition, when it introduce | transduces into an extruder (1) from a supply hopper (not shown), it is preferable to prevent oxidative decomposition etc. by making it under vacuum or pressure reduction, or inert gas atmosphere.

When additives such as plasticizer are not mixed in advance, they may be kneaded in the middle of the extruder. In order to add uniformly, it is preferable to use a mixing apparatus such as a static mixer (3).

It is preferable that a resin such as a cellulose resin and other additives such as a stabilizer added as necessary are mixed before melting. Mixing may be performed by a mixer or the like, or as described above, mixing may be performed in a resin preparation process such as a cellulose resin. When a mixer is used, a general mixer such as a V-type mixer, a conical screw type mixer, a horizontal cylindrical type mixer, or the like can be used.

After the film constituent materials are mixed as described above, the mixture may be directly melted and formed into a film using an extruder (1). Once the film constituent materials are pelletized, the pellets May be melted with an extruder (1) to form a film. Further, when the film constituent material includes a plurality of materials having different melting points, a so-called braided semi-melt is once produced at a temperature at which only a material having a low melting point is melted, and the semi-melt is extruded (1). ) To form a film. If the film component contains a material that is easily pyrolyzed, in order to reduce the number of times of melting, a method of directly forming a film without producing pellets, or after making a paste-like semi-molten material as described above A method of forming a film is preferred.

As the extruder (1), various commercially available extruders can be used, but a melt-kneading extruder is preferable, and a single-screw extruder or a twin-screw extruder may be used. When forming a film directly without producing pellets from film constituent materials, it is preferable to use a twin-screw extruder because an appropriate degree of kneading is required. However, even with a single-screw extruder, the screw shape is a Maddock type. By changing to a kneading type screw such as a unimelt type or a dull mage, moderate kneading can be obtained, so that it can be used. When a pellet or braided semi-melt is once used as a film constituent material, it can be used in either a single screw extruder or a twin screw extruder.

In the extruder (1) and after the extrusion, the cooling step is preferably performed by substituting with an inert gas such as nitrogen gas or reducing the pressure to reduce the oxygen concentration.

Although the preferable conditions for the melting temperature of the film constituent material in the extruder (1) vary depending on the viscosity and discharge amount of the film constituent material, the thickness of the sheet to be produced, etc., in general, the glass transition of the film (resin mixture) It is Tg or more and Tg + 100 ° C. or less, preferably Tg + 10 ° C. or more and Tg + 90 ° C. or less with respect to the temperature Tg.

The melt viscosity at the time of extrusion is 10 to 100,000 poise, preferably 100 to 10,000 poise. Further, the residence time of the film constituting material in the extruder (1) is preferably short, and is within 5 minutes, preferably within 3 minutes, more preferably within 2 minutes. The residence time depends on the type of the extruder (1) and the extrusion conditions, but it can be shortened by adjusting the material supply amount, L / D, screw rotation speed, screw groove depth, and the like. Is possible.

The shape and rotation speed of the screw of the extruder (1) are appropriately selected depending on the viscosity and the discharge amount of the film constituting material. In this embodiment, the shear rate in the extruder (1) is 1 / second to 10,000 / second, preferably 5 / second to 1000 / second, more preferably 10 / second to 100 / second. As the extruder (1), an extruder generally marketed as a plastic molding machine can be used.

The film constituting material extruded from the extruder (1) is sent to the casting die (4) and extruded from the casting die (4) into a film shape.

The melt discharged from the extruder (1) is supplied to the casting die (4). The casting die (4) is not particularly limited as long as it is used for producing a sheet or a film. As the material of the casting die (4), hard chromium, chromium carbide, chromium nitride, titanium carbide, titanium carbonitride, titanium nitride, super steel, ceramic (tungsten carbide, aluminum oxide, chromium oxide), etc. are sprayed or plated. Buffing as surface processing, lapping using a # 1000 or higher grinding wheel, plane cutting using a diamond grinding wheel of # 1000 or higher (cutting direction is perpendicular to the resin flow direction), electrolytic polishing, electrolytic composite polishing, etc. And the like.

The preferred material of the lip portion of the casting die (4) is the same as that of the casting die (4). The surface accuracy of the lip is preferably 0.5S or less, and more preferably 0.2S or less.

As described above, the method for producing an optical film of the present invention allows the surface of the metal support (5) made of the first cooling roll to be formed on the surface of the metal support (5) before casting the resin melt. In the position or in the non-passage section of the web on the surface of the metal support (5) during film formation (section where the surface of the metal support (5) is exposed during film formation), In the presence of a gas used for plasma irradiation or excimer ultraviolet irradiation, the surface of the metal support (5) is modified by applying a high energy surface treatment with an atmospheric pressure plasma irradiation apparatus (21) or an excimer ultraviolet irradiation apparatus (22). The resin melt is cast on the surface of the modified metal support (5).

That is, in the method for producing an optical film according to the present invention, the surface of the metal support (5) on which the resin melt is cast is so-called off-line before casting the resin melt, and the surface of the metal support (5) is predetermined. The high-energy surface treatment is performed by the atmospheric pressure plasma irradiation apparatus (21) or the excimer ultraviolet irradiation apparatus (22) in the presence of the vapor of the additive and the gas used for atmospheric pressure plasma irradiation or excimer ultraviolet irradiation. The surface of the metal support (5) is modified by the above-mentioned method, or the non-passage section of the web on the surface of the metal support (5) [metal support (5) during film formation] In the section where the surface is exposed], in the presence of the vapor of the additive and the gas used for atmospheric pressure plasma irradiation or excimer ultraviolet irradiation, the atmospheric pressure plasma irradiation apparatus (21) Alternatively, the surface of the metal support (5) is modified by applying a high energy surface treatment with an excimer ultraviolet irradiation device (22), and the resin melt is cast on the surface of the modified metal support (5). To do.

In the present embodiment, after a film material containing a resin such as cellulose ester resin is mixed to obtain a resin mixture, the first cooling roll (metal support) is formed from the casting die (4) using the extruder (1). Body) (5) is melt-extruded and brought into contact with the first cooling roll (5), and the film-like melt is pressed against the surface of the first cooling roll (5) with a predetermined pressure by the touch roll (6). Furthermore, the total of three cooling rolls of the second cooling roll (7) and the third cooling roll (8) are sequentially circumscribed and solidified by cooling, and are peeled off by the peeling roll (9). The peeled web (10) is one in which both ends of the web (10) are gripped by the tenter (11) and stretched in the width direction, and then the stretched film is wound up by the winder (12).

In the present embodiment, the temperature of the first cooling roll (5) is set to be equal to or lower than the glass transition temperature (Tg) of the resin mixture and equal to or higher than the melting point of the additive.

Moreover, in the manufacturing method of the optical film of this embodiment, ratio (S2 / S1) of the circumferential speed (S1) of the 1st cooling roll (5) and the circumferential speed (S2) of the 2nd cooling roll (7), It is preferable to set to 1.001 to 1.05.

The touch roll (6) is a rotating body intended to sandwich the film in the direction of the first cooling roll (5) from the opposite side of the first cooling roll (5) to the film.

The surface of the touch roll (6) is preferably a metal, and the thickness is 1 mm to 10 mm. It is preferably 2 mm to 6 mm. The surface of the touch roll (6) is subjected to a treatment such as chrome plating, and the surface roughness is preferably 0.2S or less. The smoother the roll surface, the smoother the surface of the resulting film.

The metal material on the surface of the touch roll (6) is required to be smooth, moderately elastic and durable. Carbon steel, stainless steel, titanium, nickel produced by electroforming, etc. can be preferably used. Further, in order to increase the hardness of the surface or improve the releasability from the resin, it is preferable to carry out a surface treatment such as hard chrome plating, nickel plating, amorphous chrome plating, or ceramic spraying. It is preferable that the surface processed is further polished to have the above-described surface roughness.

The touch roll (6) has a double structure of a metal outer cylinder and an inner cylinder, and has a structure of a double cylinder having a space so that a cooling fluid can flow between them.

The inner cylinder is preferably a lightweight and rigid metallic inner cylinder such as carbon steel, stainless steel, aluminum, titanium or the like. By giving rigidity to the inner cylinder, it is possible to suppress the rotational shake of the roll. A sufficient rigidity can be obtained by setting the thickness of the inner cylinder to 2 to 10 times that of the outer cylinder. The inner cylinder may be further coated with a resin elastic material such as silicone or fluororubber.

The structure of the space through which the cooling fluid flows can be any structure as long as the temperature of the roll surface can be uniformly controlled. For example, the roll can be made to flow in a spiral direction by flowing alternately and back in the width direction. Temperature control with a small surface temperature distribution is possible. The cooling fluid is not particularly limited, and water or oil can be used according to the temperature range to be used.

In the present embodiment, the touch roll (6) as the second rotating body is set to a drum shape in which the outer diameter of the central part is larger than the outer diameters of both end parts. The touch roll generally presses both ends of the touch roll against the film with a pressurizing unit, but in this case, the touch roll is bent, so that there is a phenomenon that the touch roll is pressed more strongly toward the end. Highly uniform pressing is possible by making the roll into a drum shape.

The diameter of the touch roll (6) as the second rotating body is preferably in the range of 200 mm to 500 mm. The effective width of the touch roll (6) needs to be wider than the film width to be pressed. Due to the difference between the radius of the center portion and the radius of the end portion of the touch roll (6) (hereinafter referred to as the crowning amount), unevenness such as streaks generated in the center portion of the film can be prevented. The amount of crowning is preferably in the range of 50 to 300 μm.

The first cooling roll (5) and the touch roll (6) are installed at positions opposite to the plane of the film so as to sandwich the film. The first cooling roll (5) and the touch roll (6) may be in contact with the film by a surface or by a line.

In the method for producing an optical film according to the present embodiment, the conditions for melt extrusion can be performed in the same manner as the conditions used for other thermoplastic resins such as polyester. The material is preferably dried beforehand. It is desirable to dry the moisture to 1000 ppm or less, preferably 200 ppm or less, using a vacuum or reduced pressure dryer or a dehumidifying hot air dryer.

In this embodiment, the molten resin mixture is extruded from a casting die (4) attached to an extruder to a film-like resin, and the extruded film-like resin is brought into close contact with at least two rotating bodies to be molded and taken out. Process.

At this time, it is preferable to press the film against the first cooling roll (5) by pressing means comprising the touch roll (6). The linear pressure with which the touch roll (6) presses the film at this time can be adjusted by a hydraulic piston or the like, and is preferably 0.1 to 100 N / mm, more preferably 1 to 50 N / mm.

Further, the first cooling roll (5) or the touch roll (6) can have a diameter reduced at both ends of the roll or can have a flexible roll surface in order to improve the uniformity of adhesion with the film.

When the portion from the opening (lip) of the casting die (4) to the first cooling roll (5) is depressurized to 70 kPa or less, the above-described die line correction effect is more greatly manifested. The reduced pressure is preferably 50 kPa or more and 70 kPa or less. There is no particular limitation on the method for maintaining the pressure in the portion from the lip of the casting die (4) to the first cooling roll (5) to 70 kPa or less, but the roll periphery from the casting die (4) is covered with a pressure-resistant member. There is a method of reducing the pressure. At this time, the suction device is preferably subjected to a treatment such as heating with a heater so that the device itself does not become a place where the sublimate is attached. If the suction pressure is too small, the sublimate cannot be sucked effectively, so it is necessary to set the suction pressure appropriately.

In the present embodiment, a film-like cellulose ester resin in a molten state from the T die (4) is in close contact with the first cooling roll (5), the second cooling roll (7), and the third cooling roll (8). The mixture is cooled and solidified while being conveyed to obtain a cellulose ester resin web (10).

In the embodiment of the present invention shown in FIG. 1, the cooled and solidified web (10) peeled from the third cooling roll (8) by the peeling roll 9 is stretched by the tenter (11). By this stretching, the molecules in the film are oriented.

The apparatus for cooling the film (resin mixture) extruded from the casting die (4) is not limited to a roll, and may be a drum or a belt.

The film (10) peeled off from the cooling roll (5) described above is a tenter (11) and is stretched in one or more stages in the longitudinal direction through one or a plurality of roll groups and / or a heating device such as an infrared heater. It is preferable to do. At this time, when the glass transition temperature of the film is Tg, it is preferably heated in the range of Tg−50 ° C. to Tg + 80 ° C. and stretched in the transport direction.

Next, the film stretched in the conveying direction is preferably stretched in the temperature range of Tg-50 ° C. to Tg + 80 ° C. and then heat-set.

The tenter (11) may be laterally stretched. In that case, when the lateral stretch is performed while sequentially raising the temperature difference in the range of 1 to 50 ° C. in the stretched region divided into two or more, the thickness in the width direction and the optical This is preferable because the distribution can be reduced.

Although Tg differs depending on the film constituent material, Tg can be controlled by varying the material type constituting the film and the ratio of the constituent materials. When a retardation film is produced as an optical film, Tg is preferably 120 ° C. or higher, preferably 135 ° C. or higher. In the liquid crystal display device, in the image display state, the temperature environment of the film changes due to the temperature rise of the device itself, for example, the temperature rise derived from the light source. At this time, when the Tg of the film is lower than the use environment temperature of the film, the retardation value derived from the orientation state of the molecules fixed inside the film by stretching and the dimensional shape as the film are greatly changed. If the Tg of the film is too high, the temperature of the film constituting material will increase when the film is made into a film, so that the energy consumption for heating will increase, and the material itself may be decomposed and colored due to film formation. Therefore, Tg is preferably 250 ° C. or less.

In the stretching process, known heat setting treatment, cooling, and relaxation treatment may be performed, and the stretching may be appropriately adjusted so as to have characteristics required for the target optical film.

When producing a retardation film, the above stretching step and heat setting treatment are appropriately selected and performed in order to provide functions and physical properties necessary for widening the viewing angle of the liquid crystal display device. That is, when producing a retardation film as an optical film and further combining the functions of a polarizing plate protective film, it is necessary to control the refractive index, but the refractive index can be controlled by a stretching operation. A stretching operation is a preferred method. Hereinafter, the stretching method will be described.

In the retardation film stretching process, the required retardation is obtained by stretching the cellulose resin by 1.0 to 3.0 times in one direction and by 1.01 to 3.5 times in the direction perpendicular to the film plane. Ro and Rt can be controlled. Here, Ro represents in-plane retardation, and is obtained by multiplying the difference between the refractive index in the longitudinal direction (MD) and the refractive index in the width direction (TD) by the thickness, and Rt is the thickness direction retardation. The difference between the in-plane refractive index (average in the longitudinal direction (MD) and the width direction (TD)) and the refractive index in the thickness direction is multiplied by the thickness.

Stretching can be performed sequentially or simultaneously, for example, in the longitudinal direction of the film (casting / conveying direction) and in the direction orthogonal to the film plane, that is, in the width direction. At this time, if the stretching ratio in at least one direction is too small, a sufficient phase difference cannot be obtained, and if it is too large, stretching becomes difficult and film breakage may occur.

Stretching in biaxial directions perpendicular to each other is an effective method for putting the refractive indexes nx, ny, and nz of the film within a predetermined range. Here, nx is the refractive index in the longitudinal (MD) direction, ny is the refractive index in the width (TD) direction, and nz is the refractive index in the thickness direction.

For example, when the film is stretched in the melt casting direction, if the shrinkage in the width direction is too large, the value of nz becomes too large. In this case, it can be improved by suppressing the width shrinkage of the film or stretching in the width direction. When stretching in the width direction, the refractive index may be distributed in the width direction. This distribution may appear when the tenter method is used. By stretching the film in the width direction, a shrinkage force is generated at the center of the film, and the phenomenon is caused by the end being fixed. It is thought to be called the Boeing phenomenon. Even in this case, by stretching in the casting direction, the bowing phenomenon can be suppressed and the distribution of the phase difference in the width direction can be reduced.

The film thickness variation of the obtained film can be reduced by stretching in the biaxial directions perpendicular to each other. When the film thickness variation of the retardation film is too large, the retardation becomes uneven, and unevenness such as coloring may be a problem when used in a liquid crystal display.

The film thickness variation of the cellulose resin film is preferably in the range of ± 3%, more preferably ± 1%. For the purposes as described above, a method of stretching in the biaxial directions perpendicular to each other is effective, and the stretching ratio in the biaxial directions perpendicular to each other is finally 1.0 to 3.0 times in the casting direction. The width is preferably in the range of 1.01 to 3.5 times, in the range of 1.01 to 2.5 times in the casting direction and 1.05 to 3.0 times in the width direction. It is more preferable to obtain the required retardation value.

After the web (10) is stretched by the tenter as described above, the end portion of the obtained web (film) is slit into a product width by a slitter and cut off, and then a knurling device comprising an embossing ring and a back roll By applying a knurling process (embossing process) to both ends of the film and winding it with a winder (13), sticking in the optical film (original winding) and scratching are prevented. The knurling method can process a metal ring having an uneven pattern on its side surface by heating or pressing. In addition, since the grip part of the clip of the both ends of a film is deform | transforming normally and cannot be used as a film product, it is cut out and reused as a raw material.

The thermoplastic resin used in the method for producing an optical film of the present invention is not particularly limited as long as it can be formed by a melt casting method. For example, cellulose ester, polycarbonate, alicyclic structure-containing polymer, polyvinyl alcohol, polyamide, polyimide, polyester and the like can be mentioned. Among them, cellulose esters and alicyclic structure-containing polymers are preferable because of their small photoelastic coefficient, and alicyclic structure-containing polymers are particularly preferable because of their low water absorption.

As the cellulose ester, cellulose acetate propionate, cellulose acetate butyrate and cellulose acetate propionate butyrate are preferable. The degree of substitution of the acetyl group of the cellulose ester is preferably at least 1.5 or more because the resulting film has excellent dimensional stability. The method for measuring the substitution degree of the acyl group of the cellulose ester can be carried out according to ASTM D-817-91. The molecular weight of the cellulose ester is preferably 50,000 to 300,000, particularly 60,000 to 200,000 as the number average molecular weight because the mechanical strength of the resulting film can be increased.

The alicyclic structure-containing polymer is a polymer having an alicyclic structure in the repeating unit, and the alicyclic structure may be in either the main chain or the side chain. Examples of the alicyclic structure include a cycloalkane structure and a cycloalkene structure, but a cycloalkane structure is preferable because of excellent thermal stability.

The alicyclic structure-containing polymer is a monomer containing a norbornene ring structure, a monocyclic olefin, a cyclic conjugated diene, a vinyl aromatic compound, a vinyl alicyclic hydrocarbon compound, or the like, such as metathesis ring-opening polymerization or addition polymerization. It can be obtained by polymerizing by a known polymerization method and, if necessary, hydrogenating a carbon-carbon unsaturated bond.

The alicyclic structure-containing polymer used in the present invention has a polyisoprene or polystyrene equivalent weight average molecular weight (Mw) of 25 measured by gel permeation chromatography of a cyclohexane solution (or a toluene solution when the polymer is not dissolved). 5,000 to 50,000, more preferably 30,000 to 45,000. The molecular weight distribution (Mw / Mn) is preferably 1.2 to 3.5, more preferably 1.5 to 3.0. The glass transition temperature (Tg) is preferably 80 to 170 ° C. By setting the characteristics of the alicyclic structure-containing polymer within the above range, good heat resistance and moldability can be obtained.

The polyester is not particularly limited, but it is preferable to use a dicarboxylic acid component and a diol component as main constituent components.

The main constituent dicarboxylic acid components include terephthalic acid, isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, diphenylsulfone dicarboxylic acid, diphenyl ether dicarboxylic acid, diphenylethanedicarboxylic acid, Examples thereof include cyclohexane dicarboxylic acid, diphenyl dicarboxylic acid, diphenyl thioether dicarboxylic acid, diphenyl ketone dicarboxylic acid, and phenylindane dicarboxylic acid. Examples of the diol component include ethylene glycol, propylene glycol, tetramethylene glycol, cyclohexanedimethanol, 2,2-bis (4-hydroxyphenyl) propane, 2,2-bis (4-hydroxyethoxyphenyl) propane, bis ( 4-Hydroxyphenyl) sulfone, bisphenol fluorene hydroxyethyl ether, diethylene glycol, neopentyl glycol, hydroquinone, cyclohexanediol and the like.

Among the polyesters comprising these as main components, terephthalic acid and / or 2,6-naphthalenedicarboxylic acid as a dicarboxylic acid component and ethylene glycol as a diol component from the viewpoints of transparency, mechanical strength, dimensional stability, etc. And / or a polyester having 1,4-cyclohexanedimethanol as a main constituent is preferred. Among them, polyesters mainly composed of polyethylene terephthalate or polyethylene-2,6-naphthalenedicarboxylate, copolymerized polyesters composed of terephthalic acid, 2,6-naphthalenedicarboxylic acid and ethylene glycol, and two of these polyesters. Polyesters containing a mixture of two or more species as main constituents are preferred. When polyethylene-2,6-naphthalenedicarboxylate is contained in an amount of 70% by weight or more based on the polyester, a polyester film having excellent transparency, mechanical strength, dimensional stability and the like can be obtained.

The polyester constituting the polyester film of the present invention may be copolymerized with other copolymer components or may be mixed with other polyesters as long as the effects of the present invention are not impaired. Examples of these include the dicarboxylic acid components and diol components mentioned above, or polyesters composed thereof.

For the purpose of improving the heat resistance of the polyester film of the present invention, a bisphenol compound, a compound having a naphthalene ring or a cyclohexane ring can be copolymerized. The copolymerization ratio of these is preferably 1 to 20 mol% based on the difunctional dicarboxylic acid constituting the polyester.
Also, two or more compatible polymers may be blended and subjected to melt kneading described later.

Hereinafter, in particular, cellulose ester will be described in detail, but the present invention is not limited thereto.

When a cellulose ester is formed into a film by the melt casting method, usually, cellulose sester remains in the cellulose ester in the course of its production, so that an acid such as alkyl carboxylic acid and sulfuric acid remains in the cellulose ester. When the film is formed by the method, coloration and viscosity decrease occur, so that optical properties and mechanical properties such as haze, transmittance, and retardation are deteriorated. Therefore, it is desirable to remove the acid to 50 ppm or less in advance.

The melt casting in the present invention is defined as melt casting in which a cellulose ester is heated and melted to a temperature exhibiting fluidity without using a solvent, and then the fluid cellulose ester is cast. The molding method for heating and melting can be further classified into a melt extrusion molding method, a press molding method, an inflation method, an injection molding method, a blow molding method, a stretch molding method, and the like. Among these, in order to obtain an optical film excellent in mechanical strength and surface accuracy, the melt extrusion method is excellent. Here, after the film constituent material is heated to express its fluidity, it is cast from a casting die onto a rotationally driven metal endless belt or a rotationally driven metal drum (metal support) to form a film. It is included in the method for producing a cellulose ester film of the present invention as a melt casting film forming method.
(Cellulose ester)
The cellulose ester used in the present invention is the above-mentioned single or mixed acid ester of cellulose containing at least one structure among a fatty acyl group and a substituted or unsubstituted aromatic acyl group.

In the aromatic acyl group, when the aromatic ring is a benzene ring, examples of the substituent of the benzene ring include halogen atom, cyano, alkyl group, alkoxy group, aryl group, aryloxy group, acyl group, carbonamido group, sulfone. Amido group, ureido group, aralkyl group, nitro, alkoxycarbonyl group, aryloxycarbonyl group, aralkyloxycarbonyl group, carbamoyl group, sulfamoyl group, acyloxy group, alkenyl group, alkynyl group, alkylsulfonyl group, arylsulfonyl group, alkyloxy A sulfonyl group, an aryloxysulfonyl group, an alkylsulfonyloxy group and an aryloxysulfonyl group, —S—R, —NH—CO—OR, —PH—R, —P (—R) ₂ , —PH—O—R, -P (-R) (-O-R), -P _{-O-R) 2, -PH (} = O) -R-P (= O) (- R) 2, -PH (= O) -O-R, -P (= O) (- R) (- O—R), —P (═O) (— O—R) ₂ , —O—PH (═O) —R, —O—P (═O) (— R) ₂ —O—PH (═O ) —O—R, —O—P (═O) (— R) (— O—R), —O—P (═O) (— O—R) ₂ , —NH—PH (═O) — R, —NH—P (═O) (— R) (— O—R), —NH—P (═O) (— O—R) ₂ , —SiH ₂ —R, —SiH (—R) ₂ , —Si (—R) ₃ , —O—SiH ₂ —R, —O—SiH (—R) ₂ , and —O—Si (—R) ₃ . R is an aliphatic group, an aromatic group or a heterocyclic group. The number of substituents is preferably 1 to 5, more preferably 1 to 4, further preferably 1 to 3, and preferably 1 or 2. Most preferred. As the substituent, a halogen atom, cyano, alkyl group, alkoxy group, aryl group, aryloxy group, acyl group, carbonamido group, sulfonamido group and ureido group are preferable, halogen atom, cyano, alkyl group, alkoxy group, An aryloxy group, an acyl group and a carbonamido group are more preferred, a halogen atom, cyano, an alkyl group, an alkoxy group and an aryloxy group are more preferred, and a halogen atom, an alkyl group and an alkoxy group are most preferred.

The halogen atom includes a fluorine atom, a chlorine atom, a bromine atom and an iodine atom. The alkyl group may have a cyclic structure or a branch. The alkyl group preferably has 1 to 20 carbon atoms, more preferably 1 to 12, more preferably 1 to 6, and most preferably 1 to 4. Examples of the alkyl group include methyl, ethyl, propyl, isopropyl, butyl, t-butyl, hexyl, cyclohexyl, octyl and 2-ethylhexyl. The alkoxy group may have a cyclic structure or a branch. The number of carbon atoms of the alkoxy group is preferably 1-20, more preferably 1-12, still more preferably 1-6, and most preferably 1-4. The alkoxy group may be further substituted with another alkoxy group. Examples of the alkoxy group include methoxy, ethoxy, 2-methoxyethoxy, 2-methoxy-2-ethoxyethoxy, butyloxy, hexyloxy and octyloxy.

The number of carbon atoms of the aryl group is preferably 6-20, and more preferably 6-12. Examples of the aryl group include phenyl and naphthyl. The number of carbon atoms in the aryloxy group is preferably 6-20, and more preferably 6-12. Examples of the aryloxy group include phenoxy and naphthoxy. The acyl group preferably has 1 to 20 carbon atoms, more preferably 1 to 12 carbon atoms. Examples of the acyl group include formyl, acetyl and benzoyl. The carbonamide group has preferably 1 to 20 carbon atoms, and more preferably 1 to 12 carbon atoms. Examples of the carbonamido group include acetamide and benzamide. The number of carbon atoms of the sulfonamide group is preferably 1-20, and more preferably 1-12. Examples of the sulfonamide group include methanesulfonamide, benzenesulfonamide and p-toluenesulfonamide. The ureido group preferably has 1 to 20 carbon atoms, more preferably 1 to 12 carbon atoms. Examples of ureido groups include (unsubstituted) ureido.

The number of carbon atoms in the aralkyl group is preferably 7-20, and more preferably 7-12. Examples of the aralkyl group include benzyl, phenethyl and naphthylmethyl. The number of carbon atoms in the alkoxycarbonyl group is preferably 1-20, and more preferably 2-12. Examples of the alkoxycarbonyl group include methoxycarbonyl. The aryloxycarbonyl group preferably has 7 to 20 carbon atoms, and more preferably 7 to 12 carbon atoms. Examples of the aryloxycarbonyl group include phenoxycarbonyl. The number of carbon atoms of the aralkyloxycarbonyl group is preferably 8-20, and more preferably 8-12. Examples of the aralkyloxycarbonyl group include benzyloxycarbonyl. The carbamoyl group preferably has 1 to 20 carbon atoms, and more preferably 1 to 12 carbon atoms. Examples of the carbamoyl group include (unsubstituted) carbamoyl and N-methylcarbamoyl. The number of carbon atoms in the sulfamoyl group is preferably 20 or less, and more preferably 12 or less. Examples of the sulfamoyl group include (unsubstituted) sulfamoyl and N-methylsulfamoyl. The acyloxy group preferably has 1 to 20 carbon atoms, more preferably 2 to 12 carbon atoms. Examples of the acyloxy group include acetoxy and benzoyloxy.

The number of carbon atoms of the alkenyl group is preferably 2-20, and more preferably 2-12. Examples of alkenyl groups include vinyl, allyl and isopropenyl. The alkynyl group has preferably 2 to 20 carbon atoms, and more preferably 2 to 12 carbon atoms. Examples of alkynyl groups include thienyl. The number of carbon atoms of the alkylsulfonyl group is preferably 1-20, and more preferably 1-12. The number of carbon atoms of the arylsulfonyl group is preferably 6-20, and more preferably 6-12. The alkyloxysulfonyl group preferably has 1 to 20 carbon atoms, and more preferably 1 to 12 carbon atoms. The number of carbon atoms in the aryloxysulfonyl group is preferably 6-20, and more preferably 6-12. The alkylsulfonyloxy group preferably has 1 to 20 carbon atoms, more preferably 1 to 12 carbon atoms. The number of carbon atoms in the aryloxysulfonyl group is preferably 6-20, and more preferably 6-12.

In the cellulose ester according to the present invention, when the hydrogen atom of the hydroxyl group of cellulose is a fatty acid ester with an aliphatic acyl group, the aliphatic acyl group has 2 to 20 carbon atoms, specifically acetyl, propionyl, Examples include butyryl, isobutyryl, valeryl, pivaloyl, hexanoyl, octanoyl, lauroyl, stearoyl and the like.

In the present invention, the aliphatic acyl group is meant to include those having a substituent, and the substituent is a substitution of a benzene ring when the aromatic ring is a benzene ring in the above-mentioned aromatic acyl group. What was illustrated as a group is mentioned.

Further, when the esterified substituent of the cellulose ester is an aromatic ring, the number of substituents X substituted on the aromatic ring is 0 or 1 to 5, preferably 1 to 3, particularly preferably. Is one or two. Further, when the number of substituents substituted on the aromatic ring is 2 or more, they may be the same or different from each other, but they may be linked together to form a condensed polycyclic compound (for example, naphthalene, indene, indane, phenanthrene, quinoline). , Isoquinoline, chromene, chroman, phthalazine, acridine, indole, indoline, etc.).

As the structure used in the cellulose ester according to the present invention, the cellulose ester has a structure having a structure selected from at least one of a substituted or unsubstituted aliphatic acyl group and a substituted or unsubstituted aromatic acyl group. These may be used alone or as a mixed acid ester of cellulose, or a mixture of two or more cellulose esters.

The cellulose ester according to the present invention is preferably at least one selected from cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate phthalate and cellulose phthalate.

As the substitution degree of the mixed fatty acid ester, more preferable cellulose acetate propionate and lower fatty acid ester of cellulose acetate butyrate have an acyl group having 2 to 4 carbon atoms as a substituent, and the substitution degree of the acetyl group is X, When the substitution degree of propionyl group or butyryl group is Y, it is a cellulose resin containing a cellulose ester that simultaneously satisfies the following formulas (I) and (II). The degree of substitution of the acetyl group and the degree of substitution of other acyl groups are determined by ASTM-D817-96.

Formula (I) 2.5 ≦ X + Y ≦ 2.9
Formula (II) 0.1 ≦ X ≦ 2.0
Of these, cellulose acetate propionate is particularly preferably used. Among them, 1.0 ≦ X ≦ 2.5 and 0.5 ≦ Y ≦ 2.5 are preferable. Cellulose esters having different degrees of substitution of acyl groups may be blended so that the entire optical film falls within the above range. The portion not substituted with the acyl group is usually present as a hydroxyl group. These can be synthesized by known methods. The method for measuring the degree of substitution of the acetyl group can be measured according to ASTM-D817-96.

The number average molecular weight of the cellulose ester used in the optical film of the present invention is preferably in the range of 60,000 to 300,000, and the resulting film has high mechanical strength and is preferred. Furthermore, 70,000 to 200,000 are preferable.

Further, the cellulose ester used in the present invention preferably has a weight average molecular weight Mw / number average molecular weight Mn ratio of 1.5 to 5.5, particularly preferably 2.0 to 5.0, The cellulose ester is preferably 2.5 to 5.0, more preferably 3.0 to 5.0.

The measuring method of a weight average molecular weight can be based on the following method.
(Molecular weight measurement method)
The molecular weight is measured using high performance liquid chromatography [gel permeation chromatograph (GPC)].

The measurement conditions are as follows.

Equipment: HLC-8220 GPC (Tosoh)
Column: TSK-SUPER HM-M (φ6.0mm × 150mm)
TSK-GuardcolumnH-H (φ4.6mm × 35mm)
Solvent: Tetrahydrofuran Flow rate: 0.6 ml / min
Temperature: 40 ° C
Sample concentration: 0.1% by mass
Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosoh Corporation) Mw = 1000000 to 500 was used. Thirteen samples are used at approximately equal intervals.

The raw material cellulose of the cellulose ester used in the present invention may be wood pulp or cotton linter, and the wood pulp may be softwood or hardwood, but softwood is more preferable. A cotton linter is preferably used from the viewpoint of peelability during film formation. The cellulose ester made from these can be mixed suitably or can be used independently.

For example, the ratio of cellulose ester derived from cellulose linter: cellulose ester derived from wood pulp (coniferous): cellulose ester derived from wood pulp (hardwood) is 100: 0: 0, 90: 10: 0, 85: 15: 0, 50:50: 0, 20: 80: 0, 10: 90: 0, 0: 100: 0, 0: 0: 100, 80:10:10, 85: 0: 15, 40:30:30.

The intrinsic viscosity of the cellulose resin is preferably 1.5 to 1.75 g / cm ³ , and more preferably 1.53 to 1.63.

In addition, the cellulose ester used in the present invention preferably has few bright spot foreign matters when formed into a film. A bright spot foreign material is an arrangement in which two polarizing plates are arranged orthogonally (crossed Nicols), a cellulose ester film is arranged between them, light from the light source is applied from one side, and the cellulose ester film is applied from the other side. This is the point where the light from the light source appears to leak when observed. At this time, the polarizing plate used for the evaluation is desirably composed of a protective film having no bright spot foreign matter, and a polarizing plate using a glass plate for protecting the polarizer is preferably used. The bright spot foreign matter is considered to be one of the causes due to the unacetylated or low acetylated cellulose contained in the cellulose ester, and use a cellulose ester with a little bright spot foreign matter (use a cellulose ester with a small dispersion of substitution degree). And filtering the melted cellulose ester, or removing the bright spot foreign matters through the filtration process in the same way once in the solution state in at least one of the process of synthesizing the cellulose ester and the process of obtaining the precipitate You can also. Since the molten resin has a high viscosity, the latter method is more efficient.

As the film thickness decreases, the number of bright spot foreign matter per unit area decreases, and as the cellulose ester content in the film decreases, the bright spot foreign matter tends to decrease. 0.01 mm or more is preferably 200 pieces / cm ² or less, more preferably 100 pieces / cm ² or less, more preferably 50 pieces / cm ² or less, and 30 pieces / cm ² or less. The number is preferably 10 pieces / cm ² or less, but most preferably none. The number of bright spots of 0.005 to 0.01 mm or less is also preferably 200 / cm ² or less, more preferably 100 / cm ² or less, and 50 / cm ² or less. The number is preferably 30 pieces / cm ² or less, more preferably 10 pieces / cm ² or less, and most preferably none.

When removing bright spot foreign matter by melt filtration, it is more effective to filter the composition mixed with a plasticizer, deterioration inhibitor, antioxidant, etc. than to filter the melted cellulose ester alone. This is preferable because of its high removal efficiency. Of course, the cellulose ester may be dissolved in a solvent during the synthesis and reduced by filtration. What mixed the ultraviolet absorber and other additives suitably can be filtered. Filtration is preferably performed with a melt containing cellulose ester having a viscosity of 10,000 P or less, more preferably 5000 P or less, even more preferably 1000 P or less, and even more preferably 500 P or less. As the filter medium, conventionally known materials such as glass fibers, cellulose fibers, filter paper, and fluorine resins such as tetrafluoroethylene resin are preferably used, and ceramics and metals are particularly preferably used. The absolute filtration accuracy is preferably 50 μm or less, more preferably 30 μm or less, still more preferably 10 μm or less, and even more preferably 5 μm or less. These can be used in combination as appropriate. The filter medium can be either a surface type or a depth type, but the depth type is preferably used because it is relatively less clogged.
(Additive)
The optical film of the present invention includes, as additives, an ester plasticizer having a structure in which an organic acid and a trihydric or higher alcohol are condensed, an ester plasticizer comprising a polyhydric alcohol and a monovalent carboxylic acid, and a polycarboxylic acid. At least one stabilizer selected from at least one plasticizer of an ester plasticizer comprising an acid and a monohydric alcohol, a phenolic antioxidant, a hindered amine light stabilizer, a phosphorus stabilizer, and a sulfur stabilizer. In addition to these, a peroxide decomposing agent, a radical scavenger, a metal deactivator, an ultraviolet absorber, a matting agent, a dye, a pigment, a plasticizer other than the above, and a hindered phenol An antioxidant other than the antioxidant may be included.

It is represented by coloring and molecular weight reduction, including decomposition reactions that have not been elucidated, such as preventing oxidation of film compositions, capturing acid generated by decomposition, and suppressing or prohibiting decomposition reactions caused by radical species due to light or heat. Additives are used in order to suppress the generation of volatile components due to deterioration or material decomposition, and to impart functions such as moisture permeability and slipperiness.

On the other hand, when the film composition is heated and melted, the decomposition reaction becomes remarkable, and this decomposition reaction may be accompanied by strength deterioration of the constituent material derived from coloring or molecular weight reduction. Moreover, generation | occurrence | production of an unfavorable volatile component may be accompanied by the decomposition reaction of a film composition.

When the film composition is heated and melted, the presence of the above-mentioned additives is excellent in terms of suppressing the deterioration of the strength based on the deterioration and decomposition of the material, or maintaining the inherent strength of the material. It is necessary that the above-mentioned additives are present from the viewpoint of producing the optical film.

In addition, the presence of the above-described additives suppresses the formation of colored substances in the visible light region at the time of heating and melting, or unfavorable performance as an optical film such as transmittance and haze value generated by mixing volatile components in the film. It is excellent in that it can suppress or eliminate.

In the present invention, the display image of the liquid crystal display image is affected when the optical film is used in the configuration of the present invention exceeding 1%, and therefore the haze value is preferably less than 1%, more preferably less than 0.5%. .

In the process of imparting retardation during film production, it is possible to suppress deterioration of the strength of the film composition or to maintain the strength inherent to the material. This is because if the film composition becomes brittle due to remarkable deterioration, breakage tends to occur in the stretching step, and the retardation value may not be controlled.

In the storage or film forming process of the above film composition, deterioration reactions due to oxygen in the air may occur at the same time. In this case, it is also preferable to embody the present invention to use the effect of reducing the oxygen concentration in the air together with the stabilizing action of the additive. This includes the use of nitrogen or argon as an inert gas as a known technique, a degassing operation under reduced pressure to vacuum, and an operation under a sealed environment, and at least one of these three methods is used in combination with the above additives. It is preferable to do. By reducing the probability that the film composition comes into contact with oxygen in the air, deterioration of the material can be suppressed, which is preferable for the purpose of the present invention.

Since the optical film of the present invention is used as a polarizing plate protective film, the above-mentioned additives are contained in the film composition from the viewpoint of improving the storage stability with time for the polarizing plate of the present invention and the polarizer constituting the polarizing plate. Preferably it is present.

In the liquid crystal display device using the polarizing plate of the present invention, the above-mentioned additives are present in the optical film of the present invention, so that the above-mentioned alteration and deterioration can be suppressed and the aging storage property of the optical film can be improved. The optical compensation design given to the lens is stabilized over a long period of time, and the display quality of the liquid crystal display device is improved.
(Antioxidant)
In the present invention, the antioxidant can be used without limitation as long as it is a compound that inactivates radicals generated in the resin or suppresses deterioration of the resin due to addition of oxygen to the radical generated in the resin. Among them, useful antioxidants include phenolic compounds, hindered amine compounds, phosphorus compounds, sulfur compounds, heat-resistant processing stabilizers, oxygen scavengers, etc. Among them, particularly phenolic compounds, hindered amines. Of these, phosphorus compounds and phosphorus compounds are preferred. By blending these compounds, it is possible to prevent coloring and strength reduction of the molded product due to heat during heat molding or thermal oxidative degradation without lowering transparency and heat resistance. These antioxidants can be used alone or in combination of two or more.

Phenolic compounds are known compounds and are described, for example, in columns 12 to 14 of US Pat. No. 4,839,405, and include 2,6-dialkylphenol derivative compounds.

Specific examples of phenolic compounds include n-octadecyl 3- (3,5-di-t-butyl-4-hydroxyphenyl) -propionate, n-octadecyl 3- (3,5-di-t-butyl-4 -Hydroxyphenyl) -acetate, n-octadecyl 3,5-di-t-butyl-4-hydroxybenzoate, n-hexyl 3,5-di-t-butyl-4-hydroxyphenylbenzoate, n-dodecyl 3,5 -Di-t-butyl-4-hydroxyphenylbenzoate, neo-dodecyl 3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, dodecyl β (3,5-di-t-butyl-4 -Hydroxyphenyl) propionate, ethyl α- (4-hydroxy-3,5-di-t-butylphenyl) isobutyrate, octadecyl Α- (4-hydroxy-3,5-di-t-butylphenyl) isobutyrate, octadecyl α- (4-hydroxy-3,5-di-t-butyl-4-hydroxyphenyl) propionate, 2- (n -Octylthio) ethyl 3,5-di-t-butyl-4-hydroxy-benzoate, 2- (n-octylthio) ethyl 3,5-di-t-butyl-4-hydroxy-phenylacetate, 2- (n- Octadecylthio) ethyl 3,5-di-t-butyl-4-hydroxyphenyl acetate, 2- (n-octadecylthio) ethyl 3,5-di-t-butyl-4-hydroxy-benzoate, 2- (2- Hydroxyethylthio) ethyl 3,5-di-t-butyl-4-hydroxybenzoate, diethyl glycol bis- (3,5-di-t-butyl-4- Hydroxy-phenyl) propionate, 2- (n-octadecylthio) ethyl 3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, stearamide N, N-bis- [ethylene 3- (3,5 -Di-t-butyl-4-hydroxyphenyl) propionate], n-butylimino N, N-bis- [ethylene 3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], 2- ( 2-stearoyloxyethylthio) ethyl 3,5-di-tert-butyl-4-hydroxybenzoate, 2- (2-stearoyloxyethylthio) ethyl 7- (3-methyl-5-tert-butyl-4-hydroxy Phenyl) heptanoate, 1,2-propylene glycol bis- [3- (3,5-di-t-butyl-4-hydroxyphene) ) Propionate], ethylene glycol bis- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], neopentyl glycol bis- [3- (3,5-di-t-butyl-) 4-hydroxyphenyl) propionate], ethylene glycol bis- (3,5-di-t-butyl-4-hydroxyphenyl acetate), glycerin-ln-octadecanoate-2,3-bis- (3 5-di-t-butyl-4-hydroxyphenyl acetate), pentaerythritol-tetrakis- [3- (3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) propionate], 1,1,1 -Trimethylolethane-tris- [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], sorbito Hexa- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], 2-hydroxyethyl 7- (3-methyl-5-tert-butyl-4-hydroxyphenyl) propionate, 2- Stearoyloxyethyl 7- (3-methyl-5-t-butyl-4-hydroxyphenyl) heptanoate, 1,6-n-hexanediol-bis [(3 ', 5'-di-t-butyl-4-hydroxy Phenyl) propionate], pentaerythritol-tetrakis (3,5-di-t-butyl-4-hydroxyhydrocinnamate). Phenol compounds of the above type are commercially available from Ciba Specialty Chemicals under the trade names “Irganox 1076” and “Irganox 1010”, for example.

In the present invention, specific examples of hindered amine compounds include bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate and bis (2,2,6,6-tetramethyl-4-piperidyl) succinate. Bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate, bis (N-octoxy-2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis (N-benzyloxy) -2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis (N-cyclohexyloxy-2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis (1,2,2, 6,6-pentamethyl-4-piperidyl) 2- (3,5-di-tert-butyl-4-hydroxybenzyl) -2-butylmalonate, bis (1-acroyl) 2,2,6,6-tetramethyl-4-piperidyl) 2,2-bis (3,5-di-t-butyl-4-hydroxybenzyl) -2-butylmalonate, bis (1,2,2 , 6,6-pentamethyl-4-piperidyl) decanedioate, 2,2,6,6-tetramethyl-4-piperidyl methacrylate, 4- [3- (3,5-di-tert-butyl-4-hydroxy Phenyl) propionyloxy] -1- [2- (3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyloxy) ethyl] -2,2,6,6-tetramethylpiperidine, 2- Methyl-2- (2,2,6,6-tetramethyl-4-piperidyl) amino-N- (2,2,6,6-tetramethyl-4-piperidyl) propionamide, tetrakis (2,2,6 , 6-Tetramethi -4-piperidyl) 1,2,3,4-butanetetracarboxylate, tetrakis (1,2,2,6,6-pentamethyl-4-piperidyl) 1,2,3,4-butanetetracarboxylate Can be mentioned. Further, it may be a polymer type compound. Specific examples include N, N ′, N ″, N ′ ″-tetrakis- [4,6-bis- [butyl- (N-methyl-2,2, 6,6-tetramethylpiperidin-4-yl) amino] -triazin-2-yl] -4,7-diazadecane-1,10-diamine, dibutylamine and 1,3,5-triazine N, N'- Polycondensate of bis (2,2,6,6-tetramethyl-4-piperidyl) -1,6-hexamethylenediamine and N- (2,2,6,6-tetramethyl-4-piperidyl) butylamine , Polycondensates of dibutylamine, 1,3,5-triazine and N, N′-bis (2,2,6,6-tetramethyl-4-piperidyl) butylamine, poly [{(1,1,3 , 3-Tetramethylbutyl) amino-1,3,5-triazine -2,4-diyl} {(2,2,6,6-tetramethyl-4-piperidyl) imino} hexamethylene {(2,2,6,6-tetramethyl-4-piperidyl) imino}], 1 , 6-hexanediamine-N, N'-bis (2,2,6,6-tetramethyl-4-piperidyl) and morpholine-2,4,6-trichloro-1,3,5-triazine Condensate, poly [(6-morpholino-s-triazine-2,4-diyl) [(2,2,6,6, -tetramethyl-4-piperidyl) imino] -hexamethylene [(2,2,6 , 6-tetramethyl-4-piperidyl) imino]], etc., high molecular weight HALS in which a plurality of piperidine rings are bonded via a triazine skeleton; dimethyl succinate and 4-hydroxy-2,2,6,6-tetramethyl- 1-piperidine etano 1,2,3,4-butanetetracarboxylic acid, 1,2,2,6,6-pentamethyl-4-piperidinol and 3,9-bis (2-hydroxy-1,1- (Dimethylethyl) -2,4,8,10-tetraoxaspiro [5,5] undecane and the like, and the like include compounds in which piperidine rings are bonded via an ester bond. It is not something. Among these, polycondensates of dibutylamine, 1,3,5-triazine and N, N′-bis (2,2,6,6-tetramethyl-4-piperidyl) butylamine, poly [{(1, 1,3,3-tetramethylbutyl) amino-1,3,5-triazine-2,4-diyl} {(2,2,6,6-tetramethyl-4-piperidyl) imino} hexamethylene {(2 , 2,6,6-tetramethyl-4-piperidyl) imino}], a polymer of dimethyl succinate and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol, etc. A molecular weight (Mn) of 2,000 to 5,000 is preferred.

Hindered phenol compounds of the above type are commercially available, for example, from Ciba Specialty Chemicals under the trade names “Tinuvin 144” and “Tinvin 770” and from Asahi Denka Kogyo Co., Ltd. under the name “ADK STAB LA-52”.

In the present invention, specific examples of the phosphorus compound include triphenyl phosphite, diphenylisodecyl phosphite, phenyl diisodecyl phosphite, tris (nonylphenyl) phosphite, tris (dinonylphenyl) phosphite, tris (2, 4-Di-tert-butylphenyl) phosphite, 10- (3,5-di-tert-butyl-4-hydroxybenzyl) -9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide , 6- [3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propoxy] -2,4,8,10-tetra-tert-butyldibenz [d, f] [1.3.2] Monophosphite compounds such as dioxaphosphepine; 4,4′-butylidene-bis (3-methyl-6-tert-butylphenol) Sulfonyl - di - tridecyl phosphite), 4,4'-isopropylidene - bis (phenyl - di - alkyl (C12 ~ C15) phosphite), and the like diphosphite compounds such as. Phosphorus compounds of the above type are commercially available, for example, from Sumitomo Chemical Co., Ltd. under the trade names “Sumizer GP”, from Asahi Denka Kogyo Co., Ltd. under the trade names “ADK STAB PEP-24G” and “ADK STAB PEP-36”. Yes.

In the present invention, specific examples of the sulfur compound include dilauryl 3,3-thiodipropionate,

dimyristyl

3,3′-thiodipropionate, distearyl 3,3-thiodipropionate,

lauryl stearyl

3,3. -Thiodipropionate, pentaerythritol-tetrakis (β-lauryl-thio-propionate), 3,9-bis (2-dodecylthioethyl) -2,4,8,10-tetraoxaspiro [5,5] undecane Etc. The above-mentioned types of sulfur compounds are commercially available, for example, from Sumitomo Chemical Co., Ltd. under the trade names “Sumilezer®TPL-R” and “Sumilezer®TP-D”.

The addition amount of the antioxidant is usually 0.01 to 25 parts by mass, preferably 0.05 to 10 parts by mass, and more preferably 0.1 to 3 parts by mass with respect to 100 parts by mass of the cellulose ester.

The antioxidant is preferably removed from impurities such as residual acids, inorganic salts, organic low molecules, etc. that are carried over from production or generated during storage, and more preferably has a purity of 99% or more. It is. Residual acid and water are preferably from 0.01 to 100 ppm, and heat degradation can be suppressed when the resin is melt cast, improving film formation stability, optical properties of the film, and mechanical properties. To do.
(Plasticizer)
In the present invention, the plasticizer preferably contains 1 to 25% by mass of an ester compound having a structure in which an organic acid and a trivalent or higher alcohol are condensed. If the amount is less than 1% by mass, the effect of adding a plasticizer is not recognized. If the amount is more than 25% by mass, bleeding out is likely to occur, and the aging stability of the film is lowered. An optical film containing 3 to 20% by mass of the plasticizer is more preferred, and an optical film containing 5 to 15% by mass is more preferred.

Generally, a plasticizer is an additive having an effect of improving brittleness or imparting flexibility by being added to a polymer, but in the present invention, a cellulose ester alone is used. A plasticizer is added to lower the melt temperature than the melt temperature, and to lower the melt viscosity of the film composition containing the plasticizer than the cellulose resin alone at the same heating temperature. Moreover, since it adds also in order to improve the hydrophilic property of a cellulose ester and to improve the water vapor transmission rate of an optical film, it has a function as a moisture permeation preventive agent.

Here, the melting temperature of the film composition means a temperature at which the material is heated and fluidity is developed. In order to melt and flow the cellulose ester, it is necessary to heat at least a temperature higher than the glass transition temperature. Above the glass transition temperature, the elastic modulus or viscosity decreases due to heat absorption, and fluidity is exhibited. However, in cellulose esters, the molecular weight of the cellulose ester may decrease due to thermal decomposition at the same time as melting at high temperatures, which may adversely affect the mechanical properties of the resulting film. Therefore, it is necessary to melt the cellulose ester at the lowest possible temperature. is there. In order to lower the melting temperature of the film composition, it can be achieved by adding a plasticizer having a melting point or glass transition temperature lower than the glass transition temperature of the cellulose ester. In particular, a polyhydric alcohol ester plasticizer having a structure in which an organic acid and a polyhydric alcohol are condensed lowers the melting temperature of the cellulose ester, has low volatility after the melt film-forming process and after production, and has good process suitability. In addition, the obtained optical film is excellent in terms of optical properties, dimensional stability and flatness.

In the present invention, the organic acid for substituting the hydroxyl group of the trivalent or higher valent alcohol may be a single type or a plurality of types.

In the present invention, the trihydric or higher alcohol compound that reacts with an organic acid to form a polyhydric alcohol ester compound is preferably a trihydric to polyhydric aliphatic polyhydric alcohol.

Examples of preferred polyhydric alcohols include the following, but the present invention is not limited to these.

Adonitol, arabitol, 1,2,4-butanetriol, 1,2,3-hexanetriol, 1,2,6-hexanetriol, glycerin, diglycerin, erythritol, pentaerythritol, dipentaerythritol, tripentaerythritol, ga Examples include lactitol, glucose, cellobiose, inositol, mannitol, 3-methylpentane-1,3,5-triol, pinacol, sorbitol, trimethylolpropane, trimethylolethane, xylitol and the like. In particular, glycerin, trimethylolethane, trimethylolpropane, and pentaerythritol are preferable.

An ester of an organic acid and a trihydric or higher polyhydric alcohol can be synthesized by a known method. For example, a method of condensing an organic acid and a polyhydric alcohol in the presence of an acid to esterify, a method of previously reacting an organic acid with an acid chloride or acid anhydride and reacting with the polyhydric alcohol, a phenyl ester of an organic acid, and There are methods of reacting polyhydric alcohols, and it is preferable to select a method with good yield appropriately depending on the target ester compound.

The molecular weight of the polyhydric alcohol ester thus obtained is not particularly limited, but is preferably 300 to 1500, and more preferably 400 to 1000. A higher molecular weight is preferred because it is less likely to volatilize, and a smaller one is preferred in terms of moisture permeability and compatibility with cellulose ester.

The optical film of the present invention may be used in combination with other plasticizers.

An ester compound comprising an organic acid and a trihydric or higher polyhydric alcohol, which is a preferred plasticizer for the present invention, is highly compatible with cellulose esters and can be added at a high addition rate. Even if an additive is used in combination, bleed-out does not occur, and other types of plasticizers and additives can be easily used as needed.

When other plasticizers are used in combination, it is preferable that a plasticizer composed of an ester compound composed of an organic acid and a trihydric or higher polyhydric alcohol is contained at least 50% by mass or more of the entire plasticizer. More preferably 70% or more, still more preferably 80% or more. If it uses in such a range, even if it uses together with another plasticizer, the fixed effect that the planarity of the cellulose ester film at the time of melt casting can be improved can be acquired.

Preferred other plasticizers include the following plasticizers.
(Ester plasticizer consisting of polyhydric alcohol and monovalent carboxylic acid, ester plasticizer consisting of polyvalent carboxylic acid and monovalent alcohol)
An ester plasticizer comprising a polyhydric alcohol and a monovalent carboxylic acid, and an ester plasticizer comprising a polyvalent carboxylic acid and a monohydric alcohol are preferred because of their high affinity with the cellulose ester.

An ethylene glycol ester plasticizer that is one of polyhydric alcohol esters: specifically, ethylene glycol alkyl ester plasticizers such as ethylene glycol diacetate and ethylene glycol dibutyrate, ethylene glycol dicyclopropylcarboxylate And ethylene glycol cycloalkyl ester plasticizers such as ethylene glycol dicyclohexylcarboxylate, and ethylene glycol aryl ester plasticizers such as ethylene glycol dibenzoate and ethylene glycol di4-methylbenzoate. These alkylate groups, cycloalkylate groups, and arylate groups may be the same or different, and may be further substituted. Moreover, the mix of an alkylate group, a cycloalkylate group, and an arylate group may be sufficient, and these substituents may couple | bond together by the covalent bond. Further, the ethylene glycol part may be substituted, the ethylene glycol ester partial structure may be part of the polymer or regularly pendant, and may be an antioxidant, an acid scavenger, an ultraviolet absorber, etc. It may be introduced into a part of the molecular structure of the additive.

Glycerin ester plasticizer that is one of polyhydric alcohol esters: Specifically, glycerol alkyl esters such as triacetin, tributyrin, glycerol diacetate caprylate, glycerol oleate propionate, glycerol tricyclopropylcarboxylate, glycerol Glycerol cycloalkyl esters such as tricyclohexylcarboxylate, glycerol aryl esters such as glycerol tribenzoate and glycerol 4-methylbenzoate, diglycerol tetraacetylate, diglycerol tetrapropionate, diglycerol acetate tricaprylate, diglycerol tetralaur Diglycerin alkyl ester such as rate, diglycerin tetracyclobutylcarboxylate, diglycerin tetracycle Diglycerol cycloalkyl esters such as pentyl carboxylate, diglycerin tetrabenzoate, diglycerin aryl ester such as diglycerin 3-methylbenzoate or the like. These alkylate groups, cycloalkylcarboxylate groups, and arylate groups may be the same or different, and may be further substituted. Moreover, the mix of alkylate group, a cycloalkyl carboxylate group, and an arylate group may be sufficient, and these substituents may couple | bond together by the covalent bond. Furthermore, the glycerin and diglycerin part may be substituted, the partial structure of the glycerin ester and the diglycerin ester may be part of the polymer or regularly pendant, and the antioxidant, acid scavenger, You may introduce | transduce into a part of molecular structure of additives, such as a ultraviolet absorber.

Specific examples of other polyhydric alcohol ester plasticizers include polyhydric alcohol ester plasticizers described in paragraph numbers [0030] to [0033] of JP-A-2003-12823.

These alkylate groups, cycloalkylcarboxylate groups, and arylate groups may be the same or different, and may be further substituted. Moreover, the mix of alkylate group, a cycloalkyl carboxylate group, and an arylate group may be sufficient, and these substituents may couple | bond together by the covalent bond. Furthermore, the polyhydric alcohol part may be substituted, and the partial structure of the polyhydric alcohol may be part of the polymer or regularly pendant, and may be an antioxidant, an acid scavenger, an ultraviolet absorber. May be introduced into a part of the molecular structure of the additive.

Among the ester plasticizers composed of the polyhydric alcohol and the monovalent carboxylic acid, alkyl polyhydric alcohol aryl esters are preferred. Specifically, the above-mentioned ethylene glycol dibenzoate, glycerin tribenzoate, diglycerin tetrabenzoate, Exemplified compound 16 described in paragraph No. [0032] of Kaikai 2003-12823 can be mentioned.

Dicarboxylic acid ester plasticizer that is one of polyvalent carboxylic acid esters: Specifically, alkyl dicarboxylic acid alkyl such as didodecyl malonate (C1), dioctyl adipate (C4), dibutyl sebacate (C8), etc. Ester plasticizers, alkyl dicarboxylic acid cycloalkyl ester plasticizers such as dicyclopentyl succinate and dicyclohexyl adipate, alkyl dicarboxylic acid aryl ester plasticizers such as diphenyl succinate and di4-methylphenyl glutarate, Cycloalkyl dicarboxylic acid alkyl ester plasticizers such as dihexyl-1,4-cyclohexanedicarboxylate and didecylbicyclo [2.2.1] heptane-2,3-dicarboxylate, dicyclohexyl-1,2-cyclobutane Zikal Cycloalkyldicarboxylic acid cycloalkyl ester plasticizers such as xylate, dicyclopropyl-1,2-cyclohexyldicarboxylate, diphenyl-1,1-cyclopropyldicarboxylate, di2-naphthyl-1,4-cyclohexane Cycloalkyl dicarboxylic acid aryl ester plasticizers such as dicarboxylate, aryl dicarboxylic acid alkyl ester plasticizers such as diethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, and di-2-ethylhexyl phthalate, dicyclopropyl phthalate , Aryl dicarboxylic acid cycloalkyl ester plasticizers such as dicyclohexyl phthalate, aryl dicarboxylic acid aryls such as diphenyl phthalate and di 4-methylphenyl phthalate Ester-based plasticizers. These alkoxy groups and cycloalkoxy groups may be the same or different, may be mono-substituted, and these substituents may be further substituted. The alkyl group and cycloalkyl group may be mixed, or these substituents may be bonded together by a covalent bond. Furthermore, the aromatic ring of phthalic acid may be substituted, and a multimer such as a dimer, trimer or tetramer may be used. In addition, the partial structure of phthalate ester may be part of the polymer or regularly pendant to the polymer, and may be part of the molecular structure of additives such as antioxidants, acid scavengers, and UV absorbers. It may be introduced.

Other polycarboxylic acid ester plasticizers include alkyl polycarboxylic acid alkyl esters such as tridodecyl tricarbarate and tributyl-meso-butane-1,2,3,4-tetracarboxylate. Plasticizers, alkylpolycarboxylic acid cycloalkylester plasticizers such as tricyclohexyl tricarbarate, tricyclopropyl-2-hydroxy-1,2,3-propanetricarboxylate, triphenyl 2-hydroxy- Alkyl polyvalent carboxylic acid aryl ester plasticizers such as 1,2,3-propanetricarboxylate, tetra-3-methylphenyltetrahydrofuran-2,3,4,5-tetracarboxylate, tetrahexyl-1,2, 3,4-cyclobutanetetracarboxylate, tetra Cycloalkyl polycarboxylic acid alkyl ester plasticizers such as til-1,2,3,4-cyclopentanetetracarboxylate, tetracyclopropyl-1,2,3,4-cyclobutanetetracarboxylate, tricyclohexyl- Cycloalkyl polycarboxylic acid cycloalkyl ester plasticizers such as 1,3,5-cyclohexyl tricarboxylate, triphenyl-1,3,5-cyclohexyl tricarboxylate, hexa-4-methylphenyl-1,2, Cycloalkyl polycarboxylic acid aryl ester plasticizers such as 3,4,5,6-cyclohexylhexacarboxylate, tridodecylbenzene-1,2,4-tricarboxylate, tetraoctylbenzene-1,2,4 Aryl, such as 5-tetracarboxylate Carboxylic acid alkyl ester plasticizers, such as tricyclopentylbenzene-1,3,5-tricarboxylate, tetracyclohexylbenzene-1,2,3,5-tetracarboxylate, etc. Plasticizers such as triphenylbenzene-1,3,5-tetracartoxylate, hexa4-methylphenylbenzene-1,2,3,4,5,6-hexacarboxylate and the like of aryl polyvalent carboxylic acid aryl ester series A plasticizer is mentioned. These alkoxy groups and cycloalkoxy groups may be the same or different, and may be monosubstituted, and these substituents may be further substituted. The alkyl group and cycloalkyl group may be mixed, or these substituents may be bonded together by a covalent bond. Furthermore, the aromatic ring of phthalic acid may be substituted, and a multimer such as a dimer, trimer or tetramer may be used. In addition, the partial structure of phthalate ester may be part of the polymer or may be regularly pendant to the polymer, and introduced into part of the molecular structure of additives such as antioxidants, acid scavengers, UV absorbers, etc. May be.

Among the ester plasticizers composed of the polyvalent carboxylic acid and the monohydric alcohol, dialkyl carboxylic acid alkyl esters are preferable, and specific examples include the dioctyl adipate and tridecyl tricarbalate.
(Other plasticizers)
Examples of other plasticizers used in the present invention further include phosphate ester plasticizers and polymer plasticizers.

Phosphate ester plasticizers: specifically, phosphoric acid alkyl esters such as triacetyl phosphate and tributyl phosphate, phosphoric acid cycloalkyl esters such as tricyclobenthyl phosphate and cyclohexyl phosphate, triphenyl phosphate, tricresyl phosphate And phosphoric acid aryl esters such as cresylphenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate, tributyl phosphate, trinaphthyl phosphate, trixylyl phosphate, tris ortho-biphenyl phosphate. These substituents may be the same or different, and may be further substituted. Moreover, the mix of an alkyl group, a cycloalkyl group, and an aryl group may be sufficient, and substituents may couple | bond together by the covalent bond.

Also, alkylene bis (dialkyl phosphate) such as ethylene bis (dimethyl phosphate), butylene bis (diethyl phosphate), alkylene bis (diaryl phosphate) such as ethylene bis (diphenyl phosphate), propylene bis (dinaphthyl phosphate), phenylene bis (dibutyl phosphate) ), Arylene bis (dialkyl phosphate) such as biphenylene bis (dioctyl phosphate), phosphate esters such as arylene bis (diaryl phosphate) such as phenylene bis (diphenyl phosphate) and naphthylene bis (ditoluyl phosphate). These substituents may be the same or different, and may be further substituted. Moreover, the mix of an alkyl group, a cycloalkyl group, and an aryl group may be sufficient, and substituents may couple | bond together by the covalent bond.

Furthermore, the phosphate ester partial structure may be part of the polymer, or may be regularly pendant, and may be introduced into part of the molecular structure of additives such as antioxidants, acid scavengers, and UV absorbers. May be. Among the above-mentioned compounds, phosphoric acid aryl ester and arylene bis (diaryl phosphate) are preferable, and specifically, triphenyl phosphate and phenylene bis (diphenyl phosphate) are preferable.

Polymer plasticizer: Specifically, aliphatic hydrocarbon polymer, alicyclic hydrocarbon polymer, acrylic polymer such as polyethyl acrylate and polymethyl methacrylate, polyvinyl isobutyl ether, poly N-vinyl pyrrolidone, etc. Examples include vinyl polymers, styrene polymers such as polystyrene and poly-4-hydroxystyrene, polybutylene succinates, polyesters such as polyethylene terephthalate and polyethylene naphthalate, polyethers such as polyethylene oxide and polypropylene oxide, polyamides, polyurethanes, and polyureas. It is done. The number average molecular weight is preferably about 1,000 to 500,000, particularly preferably 5000 to 200,000. If it is 1000 or less, a problem arises in volatility, and if it exceeds 500000, the plasticizing ability is lowered, and the mechanical properties of the cellulose ester film are adversely affected. These polymer plasticizers may be a homopolymer composed of one type of repeating unit or a copolymer having a plurality of repeating structures. Two or more of the above polymers may be used in combination.

In addition, since the optical film of the present invention has an influence as an optical application when colored, the yellowness (yellow index, YI) is preferably 3.0 or less, more preferably 1.0 or less. Yellowness can be measured based on JIS-K7103.

It is preferable that the plasticizer removes impurities such as residual acids, inorganic salts, organic low molecules, etc. that are carried over from production or generated during storage, and more preferably has a purity of 99% or more, like the cellulose ester described above. is there. Residual acid and water are preferably 0.01 to 100 ppm, and when melt-forming cellulose resin, thermal deterioration can be suppressed, and film-forming stability, optical physical properties and mechanical properties of the film are improved. .
(UV absorber)
As an ultraviolet absorber, from the viewpoint of preventing deterioration of a polarizer or a display device with respect to ultraviolet rays, the ultraviolet absorber has an excellent ability to absorb ultraviolet rays having a wavelength of 370 nm or less, and from the viewpoint of liquid crystal display properties, absorption of visible light having a wavelength of 400 nm or more is absorbed. Less is preferred. Examples include oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex compounds, etc., but benzophenone compounds and less colored benzotriazole compounds preferable. The structure of the ultraviolet absorber may be a multimer such as a dimer, trimer or tetramer in which a plurality of sites having an ultraviolet absorbing ability exist in one molecule, and JP-A-10-182621. In addition, an ultraviolet absorber described in JP-A-8-337574 and a polymer ultraviolet absorber described in JP-A-6-148430 may be used.

Specific examples of useful benzotriazole ultraviolet absorbers include 2- (2'-hydroxy-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-3 ', 5'-di-tert-butylphenyl) ) Benzotriazole, 2- (2'-hydroxy-3'-tert-butyl-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-3 ', 5'-di-tert-butylphenyl)- 5-chlorobenzotriazole, 2- (2′-hydroxy-3 ′-(3 ″, 4 ″, 5 ″, 6 ″ -tetrahydrophthalimidomethyl) -5′-methylphenyl) benzotriazole, 2,2-methylenebis ( 4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol), 2- (2′-hydride) Xy-3'-tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2- (2H-benzotriazol-2-yl) -6- (straight and side chain dodecyl) -4-methylphenol Octyl-3- [3-tert-butyl-4-hydroxy-5- (chloro-2H-benzotriazol-2-yl) phenyl] propionate and 2-ethylhexyl-3- [3-tert-butyl-4-hydroxy Examples include, but are not limited to, a mixture of -5- (5-chloro-2H-benzotriazol-2-yl) phenyl] propionate.

Further, as a commercial product, TINUVIN 109, TINUVIN 171 and TINUVIN 360 (all manufactured by Ciba Specialty Chemicals) can be used.

Specific examples of benzophenone compounds include 2,4-dihydroxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxy-5-sulfobenzophenone, bis (2-methoxy-4-hydroxy-) 5-benzoylphenylmethane) and the like, but are not limited thereto.

In the present invention, the ultraviolet absorber is preferably added in an amount of 0.1 to 20% by mass, more preferably 0.5 to 10% by mass, and further preferably 1 to 5% by mass. Two or more of these may be used in combination.

In the method for producing an optical film of the present invention, it is preferable that the boiling point of the plasticizer or the ultraviolet absorber is 300 ° C. or lower. When the boiling point temperature is 300 ° C. or lower, it is sufficient to obtain a reaction rate for forming a dense surface film in a short time when atmospheric pressure plasma irradiation or excimer ultraviolet irradiation is performed over substantially the entire width of the metal support. It is preferable that an evaporating gas concentration of a high concentration can be obtained because a surface treatment film can be more stably formed on the surface of the metal support.

Examples of such plasticizers include ester plasticizers, phosphate ester plasticizers, polymer plasticizers, and ultraviolet absorbers. Preferred examples include benzophenone compounds and benzotriazole compounds. It is preferred to include at least one compound in the additive.
(Antioxidant used during melt film formation)
Cellulose ester is preferably decomposed not only by heat but also by oxygen in a high temperature environment where melt film formation is performed. Therefore, the optical film of the present invention preferably contains an antioxidant as a stabilizer. .

The antioxidant useful in the present invention can be used without limitation as long as it is a compound that suppresses deterioration of the melt molding material due to oxygen, but among the useful antioxidants, phenolic compounds, hindered amine compounds, Examples thereof include phosphorus compounds, sulfur compounds, heat-resistant processing stabilizers, oxygen scavengers, etc. Among these, phenol compounds, hindered amine compounds, and phosphorus compounds are particularly preferable. These compounds are synonymous with the compounds described in (Antioxidant used for washing cellulose ester). By blending these compounds, it is possible to prevent coloring and strength reduction of the molded product due to heat during heat molding or thermal oxidative degradation without lowering transparency and heat resistance. These antioxidants can be used alone or in combination of two or more.

The addition amount of the antioxidant is usually 0.01 to 10 parts by mass, preferably 0.05 to 5 parts by mass, and more preferably 0.1 to 3 parts by mass with respect to 100 parts by mass of the cellulose ester.
(Acid scavenger)
The acid scavenger is an agent that plays a role of trapping an acid (protonic acid) remaining in the cellulose ester brought in from the production. When the cellulose ester is melted, side chain hydrolysis is promoted by moisture and heat in the polymer, and acetic acid and propionic acid are generated in the case of CAP. A compound having an epoxy structure, a tertiary amine, an ether structure, or the like may be used as long as it can be chemically bonded to an acid, but is not limited thereto.

Specifically, it preferably contains an epoxy compound as an acid scavenger described in US Pat. No. 4,137,201. Epoxy compounds as such acid scavengers are known in the art and are derived by condensation of diglycidyl ethers of various polyglycols, particularly about 8 to 40 moles of ethylene oxide per mole of polyglycol. Metal glycol compounds such as polyglycols, diglycidyl ethers of glycerol (eg, those conventionally used in and together with vinyl chloride polymer compositions), epoxidized ether condensation products, bisphenol A Diglycidyl ethers (ie, 4,4'-dihydroxydiphenyldimethylmethane), epoxidized unsaturated fatty acid esters (especially esters of alkyls of about 2 to 2 carbon atoms of fatty acids of 2 to 22 carbon atoms (eg Butyl epoxy stearate ), And various epoxidized long chain fatty acid triglycerides and the like (e.g., epoxidized vegetable oils and other unsaturated natural oils, which may be represented and exemplified by compositions such as epoxidized soybean oil, sometimes epoxidized natural) These are referred to as glycerides or unsaturated fatty acids and these fatty acids generally contain 12 to 22 carbon atoms)). Particularly preferred are commercially available epoxy group-containing epoxide resin compounds, EPON 815c, and other epoxidized ether oligomer condensation products.

Further possible acid scavengers that can be used include those described in paragraphs [0087] to [0105] of JP-A-5-194788.

It is preferable that the acid scavenger removes impurities such as residual acid, inorganic salt, and low molecular weight organic matter that are carried over from the production or generated during storage, and more preferably has a purity of 99%. That's it. Residual acid and water are preferably 0.01 to 100 ppm, and when melt-forming cellulose resin, thermal deterioration can be suppressed, and film-forming stability, optical physical properties and mechanical properties of the film are improved. .

The acid scavenger may be referred to as an acid scavenger, an acid scavenger, an acid catcher, etc., but can be used in the present invention without any difference due to their names.
(Viscosity reducing agent)
In the present invention, a hydrogen bonding solvent can be added for the purpose of reducing the melt viscosity. The hydrogen bonding solvent is J.I. N. As described in Israel Ativili, “Intermolecular Forces and Surface Forces” (Takeshi Kondo, Hiroyuki Oshima, Maglow Hill Publishing, 1991) and electrically negative atoms (oxygen, nitrogen, fluorine, chlorine) An organic solvent capable of producing a hydrogen atom-mediated “bond” that occurs between an electronegative atom and a covalently bonded hydrogen atom, that is, a bond having a large bonding moment and containing hydrogen, such as OH (Oxygen hydrogen bond), N—H (nitrogen hydrogen bond), FH (fluorine hydrogen bond), and an organic solvent that can arrange adjacent molecules. These have the ability to form stronger hydrogen bonds with cellulose than intermolecular hydrogen bonds of cellulose resin. In the melt casting method performed in the present invention, the glass transition temperature of the cellulose resin used alone is higher than that. The melting temperature of the cellulose resin composition can be lowered by the addition of a hydrogen bonding solvent, or the melt viscosity of the cellulose resin composition containing a hydrogen bonding solvent can be lowered at the same melting temperature as the cellulose resin. .

Examples of the hydrogen bonding solvent include alcohols such as methanol, ethanol, propanol, isopropanol, n-butanol, sec-butanol, t-butanol, 2-ethylhexanol, heptanol, octanol, nonanol, dodecanol, ethylene glycol, Propylene glycol, hexylene glycol, dipropylene glycol, polyethylene glycol, polypropylene glycol, methyl cellosolve, ethyl cellosolve, butyl cellosolve, hexyl cellosolve, glycerin, etc., ketones: acetone, methyl ethyl ketone, etc., carboxylic acids: eg formic acid, acetic acid, propionic acid, Butyric acid, etc., ethers: eg, diethyl ether, tetrahydrofuran, dioxane, etc., Pyrrolidones: eg, N-methyl Pyrrolidone, etc., amines: for example, can be exemplified trimethylamine, pyridine, etc., and the like. These hydrogen bonding solvents can be used alone or in admixture of two or more. Among these, alcohol, ketone, and ether are preferable, and methanol, ethanol, propanol, isopropanol, octanol, dodecanol, ethylene glycol, glycerin, acetone, and tetrahydrofuran are particularly preferable. Furthermore, water-soluble solvents such as methanol, ethanol, propanol, isopropanol, ethylene glycol, glycerin, acetone, and tetrahydrofuran are particularly preferable. Here, water-soluble means that the solubility in 100 g of water is 10 g or more.
(Retardation control agent)
In the optical film of the present invention, an alignment film may be formed to provide a liquid crystal layer, and polarizing plate processing may be performed in which an optical film and retardation derived from the liquid crystal layer are combined to provide optical compensation ability. As the compound to be added for controlling the retardation, an aromatic compound having two or more aromatic rings as described in EP 911,656A2 can be used as a retardation control agent. . Two or more aromatic compounds may be used in combination. The aromatic ring of the aromatic compound includes an aromatic heterocyclic ring in addition to the aromatic hydrocarbon ring. An aromatic heterocyclic ring is particularly preferred, and the aromatic heterocyclic ring is generally an unsaturated heterocyclic ring. Of these, compounds having a 1,3,5-triazine ring are particularly preferred.
(Matting agent)
In the optical film of the present invention, fine particles such as a matting agent can be added to impart slipperiness, and examples of the fine particles include inorganic compound fine particles and organic compound fine particles. The matting agent is preferably as fine as possible. Examples of the fine particles include silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, kaolin, talc, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, Examples thereof include inorganic fine particles such as magnesium silicate and calcium phosphate, and crosslinked polymer fine particles. Among these, silicon dioxide is preferable because it can reduce the haze of the film. In many cases, fine particles such as silicon dioxide are surface-treated with an organic material, but such a material is preferable because it can reduce the haze of the film.

Preferred organic substances for the surface treatment include halosilanes, alkoxysilanes, silazane, siloxane and the like. The larger the average particle size of the fine particles, the greater the sliding effect, and the smaller the average particle size, the better the transparency. The average particle size of the secondary particles of the fine particles is in the range of 0.05 to 1.0 μm. The average particle size of secondary particles of the fine particles is preferably 5 to 50 nm, more preferably 7 to 14 nm. These fine particles are preferably used in an optical film in order to generate irregularities of 0.01 to 1.0 μm on the surface of the optical film. In the present invention, the addition amount of the matting agent is preferably 0.01 to 10 g per 1 m ^{2 of} the cellulose ester film.

Examples of the fine particles of silicon dioxide include Aerosil 200, 200V, 300, R972, R972V, R974, R202, R812, OX50, TT600 manufactured by Nippon Aerosil Co., Ltd., preferably Aerosil 200V, R972, R972V, R974, R202, and R812. Two or more kinds of these fine particles may be used in combination. When using 2 or more types together, it can mix and use in arbitrary ratios. In this case, fine particles having different average particle sizes and materials, for example, Aerosil 200V and R972V can be used in a mass ratio of 0.1: 99.9 to 99.9: 0.1.

In addition, talc and glass fiber are added to increase the mechanical strength of the film and to prevent dimensional changes, and inorganic particles such as aluminum hydroxide and magnesium hydroxide are added to increase flame retardancy. May be. The shape of these additives may be any shape such as a spherical shape, a plate shape, a needle shape, a rod shape, a thread shape, and the like.

The presence of fine particles in the film used as the above addition can also be used for improving the strength of the film as another object. The presence of the fine particles in the film can also improve the orientation of the cellulose ester itself constituting the optical film of the present invention.
(Polymer material)
In the optical film of the present invention, polymer materials and oligomers other than cellulose ester may be appropriately selected and mixed. The polymer materials and oligomers described above are preferably those having excellent compatibility with the cellulose ester, and the transmittance when formed into a film is preferably 80% or more, more preferably 90% or more, and further preferably 92% or more. The purpose of mixing at least one of polymer materials and oligomers other than cellulose ester includes meanings for controlling viscosity at the time of heating and melting and improving film physical properties after film processing. In this case, it can contain as an above-mentioned other additive.

The optical film according to the present invention is manufactured by the above-described optical film manufacturing method, and the thickness of the film is preferably 30 to 200 μm.
(Polarizer)
The polarizing plate having the optical film of the present invention on at least one surface can sufficiently fulfill the important role of visualizing the change in the alignment of the liquid crystal due to the electric field.

The polarizing plate can be produced by a general method. The cellulose ester film of the present invention that has been subjected to alkali saponification treatment is bonded to at least one surface of a polarizer prepared by immersing and stretching a polyvinyl alcohol film in an iodine solution using a completely saponified polyvinyl alcohol aqueous solution. Is preferred. The cellulose ester film of the present invention may be used on the other side, or another polarizing plate protective film may be used. With respect to the cellulose ester film of the present invention, a commercially available cellulose ester film can be used as the polarizing plate protective film used on the other side. For example, as a commercially available cellulose ester film, KC8UX2M, KC4UX, KC5UX, KC4UY, KC8UY, KC12UR, KC8UY-HA, KC8UX-RHA (manufactured by Konica Minolta Opto, Inc.) and the like are preferably used. Or you may use films, such as cyclic olefin resin other than a cellulose-ester film, an acrylic resin, polyester, a polycarbonate, as a polarizing plate protective film of the other surface. In this case, since the saponification suitability is low, it is preferable to perform an adhesive process on the polarizing plate through an appropriate adhesive layer.

The polarizing plate of the present invention is obtained by using the cellulose ester film of the present invention on at least one side of a polarizer as a polarizing plate protective film. At that time, the cellulose ester film is preferably disposed so that the slow axis thereof is substantially parallel or perpendicular to the absorption axis of the polarizer.

As one polarizing plate disposed across a liquid crystal cell that is a transverse electric field switching mode type, the cellulose ester film of the present invention (particularly preferably, the cellulose ester film A described above) is disposed on the liquid crystal display cell side. It is preferred that

Examples of the polarizer preferably used in the polarizing plate of the present invention include a polyvinyl alcohol polarizing film, which includes a polyvinyl alcohol film dyed with iodine and a dichroic dye dyed. As the polyvinyl alcohol film, a modified polyvinyl alcohol film modified with ethylene is preferably used. For the polarizer, a polyvinyl alcohol aqueous solution is formed into a film and dyed by uniaxial stretching or dyed or uniaxially stretched and then preferably subjected to a durability treatment with a boron compound.

The film thickness of the polarizer is 5 to 40 μm, preferably 5 to 30 μm, and particularly preferably 5 to 20 μm. One side of the cellulose ester film of the present invention is bonded to the surface of the polarizer to form a polarizing plate. It is preferably bonded with an aqueous adhesive mainly composed of completely saponified polyvinyl alcohol or the like. Moreover, in the case of resin films other than a cellulose ester film, it can be bonded to the polarizing plate via an appropriate adhesive layer.

Since the polarizer is stretched in a uniaxial direction (usually the longitudinal direction), when the polarizing plate is placed in a high-temperature and high-humidity environment, the stretching direction (usually the longitudinal direction) shrinks, and the direction orthogonal to the stretching (usually normal) Extends in the width direction. As the thickness of the polarizing plate protective film decreases, the expansion / contraction ratio of the polarizing plate increases, and in particular, the amount of contraction in the stretching direction of the polarizer increases. Usually, the stretching direction of the polarizer is bonded to the casting direction (MD direction) of the polarizing plate protective film. Therefore, when the polarizing plate protective film is thinned, it is particularly important to suppress the stretching rate in the casting direction. . Since the cellulose ester film of the present invention is excellent in dimensional stability, it is preferably used as such a polarizing plate protective film.

The polarizing plate can be constituted by further bonding a protective film on one surface of the polarizing plate and a separate film on the opposite surface. The protective film and the separate film are used for the purpose of protecting the polarizing plate at the time of shipping the polarizing plate and at the time of product inspection.
(Liquid crystal display device)
By incorporating the polarizing plate using the optical film of the present invention into a liquid crystal display device, various liquid crystal display devices with excellent visibility can be produced. The optical film of the present invention is preferably a reflective, transmissive, transflective LCD, or TN, STN, OCB, HAN, VA (PVA, MVA), or IPS LCD. Used. In particular, in a large-screen display device having a screen size of 30 or more, particularly 30 to 54, there is no white spot at the periphery of the screen, and the effect is maintained for a long period of time. In the MVA liquid crystal display device, a remarkable effect is obtained. Is recognized. In particular, there was little color unevenness, glare and wavy unevenness, and the eyes were not tired even during long viewing. As described above, the display device having the polarizing plate of the present invention on at least one surface of the liquid crystal cell is very excellent in display quality.

Hereinafter, the present embodiment will be described more specifically by way of examples, but the present invention is not limited to these examples.
Example 1
(Resin mixture)
Cellulose acetate propionate 89% by weight
(Acetyl group substitution degree 1.4, propionyl group substitution degree 1.35,
Number average molecular weight 60000)
9% by weight of trimethylolpropane tribenzoate
(Plasticizer, melting point 85 ° C)
Antioxidant 0.25% by weight
(Product name-IRGANOX XP 420 / FD,
Ciba Specialty Chemicals)
UV absorber 1.6% by weight
(Product name-TINUVIN 928, manufactured by Ciba Specialty Chemicals, melting point 115 ° C)
Matting agent (silica fine particles) 0.15% by weight
(Product name-Sea Hoster KEP-30: Nippon Shokubai Co., Ltd.,
(Average particle size 0.3μm)
The degree of substitution of acyl groups such as acetyl group, propionyl group and butyryl group of cellulose acetate propionate was measured according to the method prescribed in ASTM-D817-96.
(Production of cellulose ester film)
After mixing the above materials with a V-type mixer for 30 minutes, a twin-screw extruder equipped with a strand die was melted at 230 ° C. in a nitrogen atmosphere to produce a cylindrical pellet having a length of 4 mm and a diameter of 3 mm. (Not shown). The obtained pellet had a glass transition temperature (Tg) of 135 ° C. as measured by a differential scanning calorimeter (DSC).

The DSC measurement was made by punching out about 10 mg of the sample with a punch, putting it in an aluminum pan, capping and crimping. This was heated at a rate of 10 ° C./min in nitrogen to a temperature condition of 30 to 250 ° C., cooled at 20 ° C./min, and again raised to 250 ° C. under the same conditions as the glass transition temperature ( Tg).

The above pellets were dried at a temperature of 100 ° C. for 5 hours to obtain a water content of 100 ppm.

Next, the pellets were supplied to the single screw extruder (1) shown in FIG. 1, and film formation was performed by a casting die (4) made of a T die.

The single-screw extruder (1) had a screw diameter of 90 mm and L / D = 30, and the screw rotation speed was adjusted so that the amount of extrusion was 140 kg / h. Nitrogen gas was sealed from the vicinity of the material supply port, and the inside of the extruder (1) was kept in a nitrogen atmosphere. The extruder (1) and the casting die (4) were each set to a temperature of 240 ° C. The casting die (4) is a coat hanger type, has a width of 1900 mm, has an inner wall plated with hard chrome, and is finished to a mirror surface with a surface roughness of 0.1S. The lip gap of the casting die (4) was set to 2 mm.

In FIG. 1, a roll having a web (10) coming out of a casting die (4) dropped onto a first cooling roll (5) having a roll surface length of 2400 mm and having a mirror surface of hard chrome plating, and simultaneously adjusted to 100 ° C. The film was pressed with a touch roll (6) having a surface length of 2400 mm.

In this embodiment, the surface of the metal support (5) made of the first cooling roll is formed on the surface of the metal support (5) made of the first cooling roll by the method of the present invention. In the non-passing section of the web (section in which the surface of the metal support (5) is exposed during film formation), the atmospheric pressure plasma irradiation device (21) called remote or downstream system shown in FIG. 2 was used. The atmospheric pressure plasma irradiation device (21) is installed on the upper side of the first cooling roll (metal support) (5) at an angle θ of 80 °.

Here, the distance (d) between the plasma gas outlet of the atmospheric pressure plasma device (21) and the first cooling roll (metal support) (5) is 5 mm, the reaction gas is only nitrogen, and the amount used is irradiation. It was set to 0.5 m ³ / min per 1 m width. The atmospheric pressure at this time was 1.0 atmospheric pressure.

The surface of the first cooling roll (metal support) (5) was subjected to atmospheric pressure plasma irradiation over substantially the entire width. Thereby, the surface treatment film was formed on the surface of the first cooling roll (5), and then the resin melt was cast on the surface of the first cooling roll (5).

In addition, the plasma blowing gas was continuously irradiated during film formation so that the irradiation time of the plasma gas on the surface of the first cooling roll (metal support) (5) was 0.1 sec.

The plasma irradiation time referred to here is the first cooling because it is difficult to measure the exact contact time between the radicals contained in the plasma blowing gas and the surface of the first cooling roll (metal support) (5). The irradiation time was defined as the time during which a certain point on the surface of the roll (metal support) (5) moved under the plasma blowing slit gap (h) by the gap. For example, when the blowing slit gap (h) is 2 mm and the peripheral speed of the first cooling roll (metal support) (5) is 2 mm / sec, the plasma irradiation time is 1 sec.

The surface temperature of the first cooling roll (5) is not higher than the glass transition temperature (Tg = 135 ° C.) of the resin, not lower than the melting point of the additive (melting point of the plasticizer is 85 ° C., and melting point of the ultraviolet absorber is 115 ° C.). It was set to 120 ° C.

Thus, according to the method of the present invention, when the atmospheric pressure plasma irradiation treatment is performed in the presence of the additive vapor and the gas used for the atmospheric pressure plasma irradiation treatment, the first cooling roll (metal support) is obtained. (5) It was confirmed that a very dense surface treatment film having a decomposition product of an additive such as a plasticizer as a constituent component was formed on the surface.

Thus, the surface treatment film formed on the surface of the first cooling roll (metal support) (5) had a contact angle of 14 degrees between the treatment film and water.

Next, a resin melt was cast on the first cooling roll (metal support) (5), and the film was pressed with a linear pressure of 5 N / mm using the touch roll (6).

The web (10) pressed by the first cooling roll (metal support) (5) and the touch roll (6) is peeled off and conveyed to the second cooling roll (7).

And by the presence of such a surface treatment film, the releasability (peelability) of the film from the surface of the first cooling roll (metal support) (5) is remarkably improved, and a very smooth peelability is obtained, The variation in the width direction of the peeling position decreased.

The film peeled off from the first cooling roll (5) is then successively circumscribed on the second cooling roll (7) and the third cooling roll (8) to be cooled and solidified, and peeled off by the peeling roll (9). To do.

Here, the ratio (S2 / S1) of the peripheral speed (S1) of the first cooling roll (5) and the peripheral speed (S2) of the second cooling roll (7) was set to 1.002.

Subsequently, both ends of the web (10) were held with a tenter and stretched in the width direction. The tenter atmosphere temperature was set to 150 ° C.

Next, the edge of the stretched cellulose acetate propionate film is slit with a slitter (not shown), and finally the cellulose acetate having a film thickness of 40 μm and a width of 2000 mm is obtained with a winder (13) having an ambient temperature of 25 ° C. The propionate film was wound up. Under these conditions, the film was formed continuously for 3 days.

Here, when the glass transition temperature (Tg) of the obtained cellulose acetate propionate film was measured in the same manner as in the case of the raw material pellets, it was 135 ° C.

It should be noted that the minimum amount of increase in peeling force necessary to peel the cast film after cooling from the surface of the first cooling roll (metal support) (5) is 24 at the start of film formation and 24 after film formation. The elapsed time was 0.3 (N / m).

About the cellulose acetate propionate film obtained by said film forming, the variation in the cross Nicol transmittance | permeability was measured as follows.
[Measurement of Cross Nicol Transmittance (CNT)]
Using a polarizing film measuring device (VAP-7070) manufactured by JASCO Corporation, at a measurement wavelength of 600 nm, crossed Nicols transmittance (CNT) at intervals of 50 mm in the width direction of the film and at intervals of 50 mm in the lengthwise direction of 300 mm. The difference between the average value of all data and the most deviated value was defined as the variation width (× 10 ⁻⁵ %) of the crossed Nicols transmittance (CNT).

According to this Example 1, the variation in transmittance at a wavelength of 600 nm at the time of crossed Nicol of the obtained cellulose acetate propionate film was 20 × 10 ⁻⁵ (%). The variation width of the crossed Nicols transmittance (CNT) serves as an index of the retardation value of the film. The smaller the variation width, the lower the retardation value of the film.

Thus, according to the method of the present invention, the variation in retardation (Re) value in the width direction and the longitudinal direction of the film and the variation in transmittance of the film are greatly reduced, and the transparency and flatness are excellent. Cellulose acetate propionate film having excellent optical properties can be produced, the production speed can be increased, the productivity of the film can be improved, and as a result, a thin film such as a protective film for a polarizing plate in recent years It was possible to meet the demands for widening, widening, and high quality.
Example 2
According to the method of the present invention, a cellulose acetate propionate film is produced in the same manner as in Example 1, except that the metal support (5) comprising the first cooling roll is different from that in Example 1 above. Before casting the resin melt, high-energy surface treatment is performed off-line at a predetermined position on the surface of the metal support (5) made of the first cooling roll by a normal pressure plasma irradiation device (21). The surface treatment film is formed on the surface of the metal support (5) made of the first cooling roll, and then the resin melt is cast on the surface of the metal support (5). is there.

That is, in Example 2, 100 g of a plasticizer, trimethylolpropane tribenzoate (melting point: 85 ° C.), was added to the hot air outlet of a hot air generator (trade name TSK-40, manufactured by Takezuna Seisakusho Co., Ltd.) with stainless steel. It is put into a fixed petri dish, and this is heated and volatilized by blowing hot air of 160 ° C. from a hot air generator, and the steam is passed through a 10 m duct wrapped with a heat insulating material through the atmospheric pressure plasma irradiation device. The atmospheric pressure plasma irradiation treatment was carried out in the presence of the additive vapor.

Thus, according to the method of the present invention of Example 2, the atmospheric pressure plasma irradiation treatment was carried out in the presence of the vapor of the additive and the gas used for the atmospheric pressure plasma irradiation treatment. The first cooling roll (metal support) (5) It was confirmed that a very dense surface treatment film having a decomposition product of an additive such as a plasticizer as a constituent component was formed on the surface.

In Example 2, the surface treatment film formed on the surface of the first cooling roll (metal support) (5) had a contact angle of 12 degrees between the treatment film and water.

Due to the presence of such a surface treatment film, the releasability (peelability) of the film from the surface of the first cooling roll (metal support) (5) is remarkably improved, and a very smooth peelability is obtained. The change in the width direction of was reduced.

The film peeled from the first cooling roll (5) is then continuously circumscribed on the second cooling roll (7) and the third cooling roll (8) in the same manner as in Example 1, and then cooled and solidified. Then, the film was peeled off by a peeling roll (9), subsequently subjected to film forming treatment, and finally a cellulose acetate propionate film having a film thickness of 40 μm and a width of 2000 mm was wound up by a winder (13). Under these conditions, the film was formed continuously for 3 days.

In Example 2, the minimum amount of increase in peeling force required to peel the cast film after cooling from the surface of the first cooling roll (metal support) (5) is as follows: It was 0.6 (N / m) at 24 hours after film formation.

According to this Example 2, the variation in transmittance at a wavelength of 600 nm at the time of crossed Nicol of the obtained cellulose acetate propionate film was 10 × 10 ⁻⁵ (%). The variation width of the crossed Nicols transmittance (CNT) serves as an index of the retardation value of the film. The smaller the variation width, the lower the retardation value of the film.
Example 3
According to the method of the present invention, a cellulose acetate propionate film is produced in the same manner as in Example 1 described above. The difference from Example 1 is that the excimer ultraviolet ray shown in FIG. The point is that the surface of the metal support (5) made of the first cooling roll is modified by the irradiation device (22).

As shown in the figure, the ultraviolet irradiation device (22) is arranged on the upper side of the first cooling roll (metal support) (5), and the ultraviolet irradiation device (22) has an irradiance of 40 mW / cm ² . An excimer ultraviolet irradiation device (22) containing Xe ₂ and an excimer ultraviolet (EUV) lamp having a wavelength of 172 nm was used. The gap (d) from the surface of the quartz glass (q) of the excimer ultraviolet lamp to the first cooling roll (metal support) (5) was set to 5 mm, and the angle θ in FIG. Further, during the film formation, a purge gas composed of nitrogen is continuously blown out, and a surface treatment film is formed on the surface of the first cooling roll (metal support) (5) by continuously irradiating with ultraviolet rays, A resin melt was cast on the surface of the metal support (5).

The surface temperature of the first cooling roll (5) is the same as in the case of Example 1 above, the glass transition temperature of the resin (Tg = 135 ° C.) or less, the melting point of the additive (the melting point of the plasticizer is 85 ° C., and It was set to 120 ° C., which is at least 115 ° C., the melting point of the ultraviolet absorber.

Thus, according to the method of the present invention, the excimer ultraviolet ray irradiation treatment was performed in the presence of the vapor of the additive and the purge gas used for the excimer ultraviolet ray irradiation treatment. As a result, the first cooling roll (metal support) (5 ) It was confirmed that a very dense surface-treated film having a decomposition product of an additive such as a plasticizer as a constituent component was formed on the surface.

Thus, the surface treatment film formed on the surface of the first cooling roll (metal support) (5) had a contact angle of 7 degrees between the treatment film and water.

In this Example 3, the minimum amount of increase in peeling force necessary to peel off the cast film after cooling from the surface of the first cooling roll (metal support) (5) is as follows: It was 0.2 (N / m) when 24 hours passed after film formation.

According to this Example 3, the variation in transmittance at a wavelength of 600 nm when the obtained cellulose acetate propionate film was crossed Nicol was 50 × 10 ⁻⁵ (%). The variation width of the crossed Nicols transmittance (CNT) serves as an index of the retardation value of the film. The smaller the variation width, the lower the retardation value of the film.
Example 4
According to the method of the present invention, a cellulose acetate propionate film is produced in the same manner as in Example 3, except that the metal support (5) comprising the first cooling roll is different from that in Example 3. Before the resin melt is cast, the surface of the metal is subjected to high energy surface treatment by an excimer ultraviolet irradiation device (22) at a predetermined position on the surface of the metal support (5) made of the first cooling roll. Thus, the surface treatment film was formed on the surface of the metal support (5) made of the first cooling roll, and then the resin melt was cast on the surface of the metal support (5).

In this example, as in Example 2 above, 100 g of the plasticizer trimethylolpropane tribenzoate (melting point: 85 ° C.) was added to a hot air generator (trade name TSK-40, Takezuna Manufacturing Co., Ltd.). Made of stainless steel in a hot air outlet, and heated and volatilized by blowing hot air of 160 ° C. from a hot air generator. Excimer ultraviolet irradiation was performed in the presence of the additive vapor in the presence of the additive vapor through the duct.

Thus, when the excimer ultraviolet irradiation treatment was performed in the presence of the vapor of the additive and the gas used for the atmospheric pressure plasma irradiation treatment, the plasticizer or the like was added to the surface of the first cooling roll (metal support) (5). It was confirmed that a very dense surface treatment film having a decomposition product of the agent as a constituent component was formed.

In Example 4, the surface treatment film formed on the surface of the first cooling roll (metal support) (5) had a contact angle of 15 degrees between the treatment film and water.

According to this Example 4, the dispersion of the transmittance at a wavelength of 600 nm at the time of crossed Nicol of the obtained cellulose acetate propionate film was 30 × 10 ⁻⁵ (%). The variation width of the crossed Nicols transmittance (CNT) serves as an index of the retardation value of the film. The smaller the variation width, the lower the retardation value of the film.

In this Example 4, the minimum amount of increase in peeling force necessary to peel off the cast film after cooling from the surface of the first cooling roll (metal support) (5) is as follows: It was 0.5 (N / m) when 24 hours passed after film formation.
Comparative Example 1
In the melt casting film forming apparatus, cellulose acetate propionate is not provided on the surface of the first cooling roll (metal support) (5) without installing a high energy irradiation processing apparatus comprising an atmospheric pressure plasma apparatus or an ultraviolet irradiation apparatus. Film formation was performed using the same materials as in Example 1.

In Comparative Example 1, the contact angle between the surface of the first cooling roll (metal support) (5) and water was 98 degrees.

In Comparative Example 1, the obtained cellulose acetate propionate film had a transmittance variation of 130 × 10 ⁻⁵ (%) at a wavelength of 600 nm when crossed Nicol, and retardation in the width direction and the longitudinal direction of the film. The variation in (Re) value was also large.

Furthermore, in this comparative example 1, the minimum increase in peel force necessary for peeling the cast film (10) after cooling from the surface of the metal support (5) is the same as that at the start of film formation. It was 14.5 (N / m) when 24 hours passed after the film formation.

Thus, according to Comparative Example 1, the peeling position where the film peels off from the first cooling roll (5) starts to fluctuate up and down after several hours from the start of film formation, and after about 24 hours, the peeling position becomes When it fluctuates, a line-like deformation extending in the width direction, which appears to have been produced, can be confirmed by visual inspection, and since quality deterioration is significant, production is stopped and cleaning work takes about a day. Productivity was considerably low.
(Preparation of polarizing plate)
Next, polarizing plates were produced using the cellulose acetate propionate films produced in Examples 1 to 4 of the present invention and Comparative Example 1.
(Polarizing film)
First, a long polyvinyl alcohol film having a thickness of 120 μm was uniaxially stretched (temperature: 110 ° C., stretch ratio: 5 times). This was immersed in an aqueous solution composed of 0.075 g of iodine, 5 g of potassium iodide, and 100 g of water for 60 seconds, and then immersed in an aqueous solution at 68 ° C. composed of 6 g of potassium iodide, 7.5 g of boric acid, and 100 g of water. . This was washed with water and dried to obtain a long polarizing film.
(Polarizer)
Next, the polarizing film and the cellulose acetate propionate film prepared in Examples 1 to 4 and Comparative Example 1 were bonded together according to the following steps 1 to 5 to prepare a polarizing plate.

Step 1: The long cellulose acetate propionate film prepared in Examples 1 to 4 and Comparative Example 1 was immersed in a 2 mol / L sodium hydroxide solution at a temperature of 50 ° C. for 90 seconds, then washed with water and dried. I let you.

Meanwhile, a commercially available long cellulose ester film was immersed in a 2 mol / L sodium hydroxide solution at a temperature of 50 ° C. for 90 seconds, then washed with water and dried.

Step 2: The long polarizing film was immersed in a polyvinyl alcohol adhesive tank having a solid content of 2% by mass for 1 to 2 seconds.

Step 3: Excess adhesive adhered to the polarizing film in Step 2 was lightly removed, and the long cellulose acetate propionate films of Examples 1 to 4 and Comparative Example 1 which were alkali-treated in Step 1 were commercially available. It was sandwiched with a long cellulose ester film and laminated.

Step 4: These films were laminated together at a speed of about 2 m / min at a pressure of 20-30 N / cm ² with two rotating rollers. At this time, care was taken to prevent bubbles from entering.

Step 5: The film sample produced in Step 4 was dried for 2 minutes in a dryer at 80 ° C. to produce a polarizing plate.
(Production of liquid crystal display panel)
The polarizing plate on the outermost surface of a commercially available liquid crystal display panel (NEC color liquid crystal display, MultiSync, LCD1525J, model name LA-1529HM) was carefully peeled off, and the polarizing plates of Examples 1 to 4 and Comparative Example 1 described above were polarized. A liquid crystal display panel was produced by pasting in the same direction.
(Visual evaluation of polarizing plate)
The evaluation described above was performed by the method shown below.
Moreover, the unevenness | visual_observation by visual observation of the polarizing plate which used these optical films as a protective film was performed as follows, and the obtained result was shown in following Table 1.

Each liquid crystal display panel produced using the cellulose acetate propionate films according to Examples 1 to 4 and Comparative Example 1 as described above looks whitish when viewed from the front and obliquely by a plurality of evaluators. Color unevenness was observed and evaluated as a polarizing plate.

○: None of the evaluators can see the color unevenness at all. △: The evaluator may slightly see the color unevenness.
Level that can be used as a product ×: Level at which many evaluators can confirm color unevenness and cannot be used as a product In addition to the evaluation of color unevenness, polarizing plate manufacturing process 1 after preparing 20 polarizing plates The degree of soiling of the alkali saponification solution was also observed.

As a result, in Examples 1 to 4 of the present invention, high energy irradiation comprising an atmospheric pressure plasma irradiation device (21) or an ultraviolet irradiation device (22) is provided near the surface of the first cooling roll (metal support) (5). A processing device is installed, and a surface treatment film is formed on the surface of the metal support (5) by performing high energy irradiation treatment on the surface of the first cooling roll (5), and then the surface of the metal support (5). According to the cellulose acetate propionate film produced by casting a resin melt on the surface, the release property (peelability) of the film from the metal support (5) is improved, and very smooth peeling is achieved. The cellulose acetate propionate film greatly reduces the variation in transmittance at a wavelength of 600 nm at the time of crossed nicols because the fluctuation in the width direction of the peeling position is reduced. To, and variations in retardation (Re) value is greatly reduced, the transparency was achieved, and excellent flatness. Furthermore, even when the cellulose acetate propionate film produced by the method of the present invention was used as a polarizing plate protective film, and even after processing into a polarizing plate, color unevenness that looked whitish was not confirmed, It became possible, and productivity could be greatly increased.

On the other hand, in Comparative Example 1, the release property (peelability) of the film from the metal support (5) is improved, a very smooth peelability is obtained, and the variation in the width direction of the peel position is reduced. Therefore, the cellulose acetate propionate film had a large variation in transmittance at a wavelength of 600 nm during crossed Nicol, a large variation in retardation (Re) value, and was inferior in transparency and flatness.

In addition, the cellulose acetate propionate film produced by the method of Comparative Example 1 was used as a polarizing plate protective film, and even after processing into a polarizing plate, white streaks were clearly seen in the crossed Nicol state with the polarizing film, and quality degradation was observed. Since it was remarkable, production had to be stopped and cleaning work for about one day had to be carried out, and the productivity was considerably low.

In addition, the manufacturing method of the optical film according to the present invention, the optical film, the polarizing plate, and the detailed configuration and the detailed operation of each component constituting the display device can be appropriately changed without departing from the spirit of the present invention. is there.

1: Extruder 2: Filter 3: Static mixer 4: Casting die 5: First cooling roll 6: Touch roll 7: Second cooling roll 8: Third cooling roll 9: Peeling roll 10: Web (film)
11: Tenter 12: Winder 21: Atmospheric plasma irradiation device 22: Excimer ultraviolet irradiation device a, b: Electrode g: Reaction gas d: Gap between surface treatment device and film h: Plasma gas blowing slit gap p: Purge gas r: reflector u: ultraviolet lamp q: quartz glass

Claims

A method for producing an optical film by a melt casting film forming method, comprising: casting a resin melt containing a thermoplastic resin and an additive on a surface of a metal support to form a casting film; and After the film is cooled and solidified, it is peeled off from the metal support, and is carried out in the presence of the additive vapor and a gas used for normal pressure plasma irradiation or excimer ultraviolet irradiation. And a step of forming a surface treatment film on the surface of the metal support over substantially the entire width of the metal support by irradiation treatment.
The step of forming a surface treatment film on the surface of the metal support is performed before casting the resin melt on the surface of the metal support, and after forming the surface treatment film on the surface of the metal support in advance. The method for producing an optical film according to claim 1, wherein the cast film is formed.
The step of forming a surface treatment film on the surface of the metal support includes the step of casting the resin melt on the surface of the metal support in a non-passing section of the casting film on the surface of the metal support. The method for producing an optical film according to claim 1, which is performed simultaneously.
The position where the atmospheric pressure plasma irradiation treatment or the excimer ultraviolet irradiation treatment is performed is near the position where the vapor of the additive is present and the resin solution is cast on the surface of the metal support. The method for producing an optical film according to claim 2.
The method for producing an optical film according to any one of claims 1 to 4, wherein the vapor is a vapor of a plasticizer or an ultraviolet absorber.
The room temperature plasma irradiation treatment is characterized in that, as a treatment condition, the power supplied between the electrodes is 1 W / cm 2 or more and 50 W / cm 2 or less (area in which discharge occurs). 6. The method for producing an optical film according to any one of 5 above.
6. The excimer ultraviolet irradiation treatment according to claim 1, wherein, as a processing condition, ultraviolet light having a dominant wavelength of 172 nm is irradiated with a light amount of 1 to 3,000 mJ / cm 2 . Manufacturing method of optical film.
8. The method for producing an optical film according to claim 1, wherein the surface treatment film has a contact angle of 5 to 40 degrees between the surface treatment film and water.
The method for producing an optical film according to any one of claims 1 to 8, wherein the thermoplastic resin is a cellulose ester resin.
The method for producing an optical film according to any one of claims 1 to 9, wherein the metal support is any one of an endless belt, a drum, and a roll for film formation.
The minimum amount of increase in peeling force necessary to peel the cast film after cooling from the surface of the metal support is 0.1 to 2 at the start of film formation and after 24 hours from film formation. It exists in the range of 2.0 (N / m), The manufacturing method of the optical film of any one of Claim 1 to 10 characterized by the above-mentioned.
An optical film manufactured by the method for manufacturing an optical film according to any one of claims 1 to 11.
13. The optical system according to claim 12, wherein the optical film has a variation in transmittance at a wavelength of 600 nm in a crossed Nicol range of 2 × 10 −5 to 60 × 10 −5 (%). the film.
A polarizing plate comprising the optical film according to claim 12 or 13 on at least one surface.
A display device comprising the polarizing plate according to claim 14.